Filed pursuant to Rule 424(b)(5)
Registration No. 333-211829

This preliminary prospectus supplement relates to an effective registration statement under the Securities Act of 1933, as amended, but is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities in any jurisdiction where the offer or sale is not permitted, and they are not soliciting an offer to buy these securities where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED March 12, 2019.

PROSPECTUS SUPPLEMENT TO

PROSPECTUS DATED JUNE 3, 2016

$                

American Tower Corporation

$                         % Senior Notes due 2024

$                         % Senior Notes due 2029

We are offering $         of     % Senior Notes due 2024 (the “2024 notes”) and $         of     % Senior Notes due 2029 (the “2029 notes” and, collectively with the 2024 notes, the “notes”). We will pay cash interest on the 2024 notes on May 15 and November 15 of each year, beginning on November 15, 2019. We will pay cash interest on the 2029 notes on March 15 and September 15 of each year, beginning on September 15, 2019. The 2024 notes will mature on May 15, 2024, and the 2029 notes will mature on March 15, 2029.

The notes will be general, unsecured obligations of American Tower Corporation and will rank equally in right of payment with all other senior unsecured debt obligations of American Tower Corporation. The notes will be structurally subordinated to all existing and future indebtedness and other obligations of our subsidiaries.

We may redeem the notes at any time, in whole or in part, in cash at the applicable redemption prices described under the heading “Description of Notes—Optional Redemption.”

The notes will not be listed on any securities exchange. Currently, there is no public market for the notes.

Investing in the notes involves risks. See “Risk Factors” beginning on page S-8 and those described as risk factors in Part I, Item 1A of our Annual Report on Form 10-K for the year ended December 31, 2018 (the “2018 Annual Report”).

Neither the Securities and Exchange Commission (the “SEC”) nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The underwriters expect to deliver the notes in book-entry form only through the facilities of The Depository Trust Company for the accounts of its participants, including Clearstream Banking, société anonyme (“Clearstream”), and Euroclear Bank S.A./N.V. (the “Euroclear Operator”), as operator of the Euroclear System (“Euroclear”), against payment on March     , 2019, which is the third business day following the date of this prospectus supplement (this settlement cycle being referred to as “T+3”). Under Rule 15c6-1 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), trades in the secondary market generally are required to settle in two business days, unless the parties to the trade expressly agree otherwise. Accordingly, purchasers who wish to trade the notes on the date of this prospectus supplement will be required, by virtue of the fact that the notes initially will settle in T+3, to specify an alternate settlement cycle at the time of any such trade to prevent a failed settlement and should consult their own advisors.

Joint Book-Running Managers

The date of this prospectus supplement is March     , 2019.

TABLE OF CONTENTS

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We are responsible for the information contained and incorporated by reference in this prospectus supplement and the accompanying prospectus. We have not, and the underwriters have not, authorized anyone to give you any other information, and we take no responsibility for any other information that others may give you. We are not making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should not assume that the information contained or incorporated by reference in this prospectus supplement or accompanying prospectus is accurate as of any date other than the date of the document containing the information.

ABOUT THIS PROSPECTUS SUPPLEMENT

This document consists of two parts. The first part is this prospectus supplement, which describes the specific terms of this offering. The second part is the accompanying prospectus, which describes more general information, some of which may not apply to this offering. You should read both this prospectus supplement and the accompanying prospectus, together with the documents incorporated by reference and the additional information described below under the heading “Where You Can Find More Information.”

If the description of the offering varies between this prospectus supplement and the accompanying prospectus, you should rely on the information in this prospectus supplement.

Any statement made in this prospectus supplement or in a document incorporated or deemed to be incorporated by reference in this prospectus supplement will be deemed to be modified or superseded for purposes of this prospectus supplement to the extent that a statement contained in this prospectus supplement or in any other subsequently filed document that is also incorporated or deemed to be incorporated by reference in this prospectus supplement modifies or supersedes that statement. Any statement so modified or superseded will not be deemed, except as so modified or superseded, to constitute a part of this prospectus supplement.

NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement and the accompanying prospectus contain or incorporate by reference statements about future events and expectations, or forward-looking statements, all of which are inherently uncertain. We have based those forward-looking statements on our current expectations and projections about future results. When we use words such as “anticipate,” “intend,” “plan,” “forecast,” “project,” “believe,” “estimate,” “expect,” “should,” “would,” “could,” “may” or similar expressions, we are making forward-looking statements. Examples of forward-looking statements include statements we make regarding future prospects of growth in the communications site leasing industry, the level of future expenditures by companies in this industry and other trends in this industry, the effects of consolidation among companies in our industry and among our tenants and other competitive and financial pressures, changes in zoning, tax and other laws and regulations, economic, political and other events, particularly those relating to our international operations, our future capital expenditure levels, the impact of technology changes on our industry and our business, our ability to maintain or increase our market share, our plans to fund our future liquidity needs, our substantial leverage and debt service obligations, our future financing transactions, our future operating results, our ability to remain qualified for taxation as a real estate investment trust for U.S. federal income tax purposes (“REIT”), the amount and timing of any future distributions including those we are required to make as a REIT, natural disasters and similar events and our ability to protect our rights to the land under our towers. These statements are based on our management’s beliefs and assumptions, which in turn are based on currently available information. These assumptions could prove inaccurate. See “Risk Factors.” These forward-looking statements may be found in this prospectus supplement and the accompanying prospectus generally as well as the documents incorporated by reference.

You should keep in mind that any forward-looking statement we make in this prospectus supplement, the accompanying prospectus, the documents incorporated by reference or elsewhere speaks only as of the date on

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which we make it. New risks and uncertainties arise from time to time, and it is impossible for us to predict these events or how they may affect us. In any event, these and other important factors, including those set forth under the caption “Risk Factors” in this prospectus supplement, in the accompanying prospectus and the documents incorporated by reference, may cause actual results to differ materially from those indicated by our forward-looking statements. We have no duty, and do not intend, to update or revise the forward-looking statements we make in this prospectus supplement, the accompanying prospectus, the documents incorporated by reference or elsewhere, except as may be required by law. In light of these risks and uncertainties, you should keep in mind that the future events or circumstances described in any forward-looking statement we make in this prospectus supplement, the accompanying prospectus, the documents incorporated by reference or elsewhere might not occur.

MARKET AND INDUSTRY DATA

This prospectus supplement and the accompanying prospectus contain or incorporate by reference estimates regarding market data, which are based on our internal estimates, independent industry publications, reports by market research firms and/or other published independent sources. In each case, we believe these estimates are reasonable. However, market data is subject to change and cannot always be verified with complete certainty due to limits on the availability and reliability of raw data, the voluntary nature of the data gathering process and other limitations and uncertainties inherent in any statistical survey of market data. As a result, you should be aware that market data set forth in this prospectus supplement, accompanying prospectus or incorporated by reference, and estimates and beliefs based on such data, may not be reliable.

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RISK FACTORS

You should carefully consider the following risk factors, in addition to the other information presented and incorporated by reference in this prospectus supplement and the accompanying prospectus, in evaluating us, our business and an investment in the notes. A description of the risks related to our business is included in the “Risk Factors” section in Part I, Item 1A of the 2018 Annual Report, which is incorporated by reference herein. The risks and uncertainties described below and incorporated by reference are not the only ones we face. Additional risks and uncertainties that we do not currently know about, or that we currently believe are immaterial, may also adversely impact our business. Events relating to any of the following risks as well as other risks and uncertainties could seriously harm our business, financial condition and results of operations. In such a case, the trading value of the notes could decline, or we may be unable to meet our obligations under the notes, which in turn could cause you to lose all or part of your investment.

Risks related to this offering

Our leverage and debt service obligations may materially and adversely affect us.

We have a substantial amount of indebtedness. As of December 31, 2018, after giving effect to the transactions described under “Capitalization,” we would have had approximately $         billion of consolidated debt and the ability to borrow additional aggregate amounts of approximately $         billion under the 2013 Credit Facility and the 2014 Credit Facility, net of approximately $10.0 million of outstanding undrawn letters of credit. Our substantial level of indebtedness increases the possibility that we may be unable to generate cash sufficient to pay when due the principal of, interest on, or other amounts due with respect to, our indebtedness. We are also permitted, subject to certain restrictions under our existing indebtedness, to obtain additional long-term debt and working capital lines of credit to meet future financing needs. This would effectively increase our total leverage. Furthermore, the indenture relating to the notes does not prohibit us from incurring additional indebtedness. Our leverage could have significant negative consequences on our financial condition and results of operations, including:

Our holding company structure results in structural subordination of the notes and may affect our ability to make payments on the notes.

The notes will be obligations exclusively of American Tower Corporation and not of our subsidiaries. However, all of our operations are conducted through our subsidiaries. Our cash flow and our ability to service our debt, including the notes, is dependent upon distributions of earnings, loans or other payments by our subsidiaries to us. Our subsidiaries are separate and distinct legal entities and have no obligation to pay any amounts due on the

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notes or to provide us with funds for our payment obligations, whether by dividends, distributions, loans or otherwise. Payments to us by our subsidiaries are contingent upon our subsidiaries’ earnings and cash flows. Moreover, our subsidiaries may incur indebtedness that may restrict or prohibit the making of distributions, the paying of dividends or the making of loans by such subsidiaries to us. The notes are structurally subordinated to all existing, and will be structurally subordinated to all future, indebtedness and other obligations issued by our subsidiaries. Certain of our subsidiary indebtedness is also secured. As of December 31, 2018, after giving effect to the transactions described under “Capitalization,” our subsidiaries would have had approximately $3.2 billion of total debt obligations (excluding intercompany obligations), including:

In the event of our insolvency, liquidation or reorganization, or should any of the indebtedness of our subsidiaries be accelerated because of a default, the holders of those debt obligations would have a claim to the proceeds from any liquidation of, or distribution from, certain of our subsidiaries prior to a claim by holders of the notes.

There may be no public market for the notes offered hereby.

Prior to the sale of the notes offered by this prospectus supplement, there has been no public market for the notes and we cannot assure you as to:

If a market were to exist for the notes, the notes could trade at prices that are lower than the principal amount of your purchase price, depending on many factors, including prevailing interest rates, the market for

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similar notes and our financial performance. We do not intend to apply for listing of the notes on any securities exchange or any automated dealer quotation system.

The underwriters have advised us that they presently intend to make a market in the notes. The underwriters are not obligated, however, to make a market in the notes, and may discontinue any such market-making at any time at their sole discretion. In addition, any market-making activity will be subject to the limits imposed by securities laws. Accordingly, we cannot assure you as to the development or liquidity of any market for the notes.

We may be unable to repay the notes when due or repurchase the notes when we are required to do so and holders may be unable to require us to repurchase their notes in certain circumstances.

At final maturity of the notes or in the event of acceleration of the notes following an event of default, the entire outstanding principal amount of the notes will become due and payable. Upon the occurrence of a Change of Control Triggering Event (as described in this prospectus supplement), we will be required to offer to repurchase in cash all outstanding notes at a redemption price equal to 101% of the principal amount of the notes plus accrued and unpaid interest, if any, up to, but not including, the repurchase date. If we were unable to make the required payments or repurchases of the notes, it would constitute an event of default under the notes and, as a result, may constitute an event of default under the 2013 Credit Facility, the 2014 Credit Facility and other outstanding indebtedness. The indentures for our other outstanding indebtedness also provide for repurchase rights upon a change of control and, in some cases, other fundamental changes under different terms. As a result, holders of our other indebtedness may have the ability to require us to repurchase their debt securities before the holders of the notes would have such repurchase rights. It is possible that we will not have sufficient funds at maturity, upon acceleration or at the time of the Change of Control Triggering Event or other fundamental change to make the required repurchase of notes and other indebtedness. In addition, a Change of Control (as described in this prospectus supplement) and certain other change of control events may constitute an event of default under the 2013 Credit Facility and the 2014 Credit Facility.

Holders may not be able to require us to purchase their notes in certain circumstances involving a significant change in the composition of our board of directors, including a proxy contest where our board of directors does not endorse the dissident slate of directors but approves them as Continuing Directors (as described in this prospectus supplement). In this regard, a decision of the Delaware Chancery Court (not involving us or our securities) considered a change of control redemption provision of an indenture governing publicly traded debt securities that is substantially similar to the change of control event described in clause (3) of the definition of “Change of Control.” In its decision, the court noted that a board of directors may “approve” a dissident stockholder’s nominees solely for purposes of such an indenture, provided the board of directors determines in good faith that the election of the dissident nominees would not be materially adverse to the interests of the corporation or its stockholders (without taking into consideration the interests of the holders of debt securities in making this determination). See “Description of Notes—Repurchase of Notes Upon a Change of Control Triggering Event.”

The notes will effectively rank junior to any secured indebtedness we incur in the future.

The notes will be our general unsecured obligations, and will effectively rank junior to any secured indebtedness we incur in the future to the extent of the assets securing such indebtedness. In the event of our bankruptcy, liquidation, reorganization or other winding up, our assets that secure indebtedness will be available to pay obligations on the notes only after all such secured indebtedness has been repaid in full from such assets. As a result, there may not be sufficient assets remaining to pay amounts due on any or all of the notes then outstanding.

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USE OF PROCEEDS

We expect that the net proceeds of this offering will be approximately $            , after deducting discounts and commissions payable to the underwriters and estimated expenses of this offering payable by us. We intend to use the net proceeds to repay existing indebtedness, including under the 2013 Credit Facility and the 2014 Credit Facility. Pending use, the net proceeds may be invested temporarily in short-term marketable securities. Our management will have broad discretion in the application of the net proceeds, and the purposes for which the net proceeds are used may change from those described above.

The 2013 Credit Facility matures on June 28, 2022, includes two optional renewal periods and currently bears interest at a rate equal to 1.125% above the London Interbank Offered Rate (“LIBOR”). The 2014 Credit Facility matures on January 31, 2024, includes two optional renewal periods and currently bears interest at a rate equal to 1.125% above LIBOR. Borrowings under the 2013 Credit Facility were primarily used to fund recent acquisitions, to repay existing indebtedness and for general corporate purposes. Borrowings under the 2014 Credit Facility were primarily used to repay existing indebtedness. Amounts outstanding under the 2013 Credit Facility and the 2014 Credit Facility that are repaid may be reborrowed at a later date. See “Capitalization.”

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CAPITALIZATION

The following table shows our cash and cash equivalents and capitalization as of December 31, 2018:

In addition, we have the ability to borrow additional amounts under the 2013 Credit Facility and the 2014 Credit Facility. You should read the capitalization table below in conjunction with “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and our consolidated financial statements and related notes, which are incorporated by reference in this prospectus supplement.

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DESCRIPTION OF NOTES

You can find the definitions of certain terms used in this description under the subheading “— Certain Definitions.” In this description, the references to “American Tower,” “we,” “us” or “our” refer only to American Tower Corporation (and not to any of its affiliates, including Subsidiaries, as defined below). The following description supplements and, to the extent inconsistent therewith, replaces the description of the general terms and provisions of the debt securities set forth in the accompanying prospectus.

American Tower Corporation will issue the notes under an indenture dated as of May 23, 2013, between us and U.S. Bank National Association, as trustee, as supplemented by a supplemental indenture thereto, relating to the notes. We refer to the indenture as so supplemented as the “indenture.” The terms of the notes include those stated in the indenture and those made part of the indenture by reference to the Trust Indenture Act of 1939, as amended (the “Trust Indenture Act”).

The following description is a summary of the material provisions of the indenture and does not restate the indenture in its entirety. We urge you to read the indenture because the indenture, and not this description, defines your rights as a holder of the notes. Copies of the indenture are available from the trustee and a copy has been filed with the registration statement of which the accompanying prospectus is a part, as set forth below under “Where You Can Find More Information.” We use certain defined terms in this description that are not defined below under “— Certain Definitions” or elsewhere in this description; these terms have the meanings assigned to them in the indenture.

General

We will issue $             aggregate principal amount of the 2024 notes and $             aggregate principal amount of the 2029 notes in this offering.

The notes will be issued in minimum denominations of $2,000 and multiples of $1,000 thereafter.

We may, without the consent of the holders of the notes, issue additional notes having the same ranking, interest rate, maturity and other terms as the notes previously issued. Any additional notes having such similar terms, together with the notes previously issued, will constitute a single series of notes under the indenture.

The 2024 notes will mature on May 15, 2024. The 2029 notes will mature on March 15, 2029. Accrued and unpaid interest on the 2024 notes will be payable in U.S. Dollars semi-annually in arrears on May 15 and November 15 of each year, which we refer to as “interest payment dates,” beginning on November 15, 2019 to the persons in whose names the 2024 notes are registered at the close of business on the preceding May 1 and November 1, respectively, which we refer to as “record dates.” Accrued and unpaid interest on the 2029 notes will be payable in U.S. Dollars semi-annually in arrears on March 15 and September 15 of each year, which we refer to as “interest payment dates,” beginning on September 15, 2019 to the persons in whose names the 2029 notes are registered at the close of business on the preceding March 1 and September 1, respectively, which we refer to as “record dates.” Interest on the notes will accrue from March     , 2019 and will be computed on the basis of a 360-day year comprised of twelve 30-day months.

Each payment of interest on the notes will include interest accrued through the day before the applicable interest payment date. Any payment required to be made on any day that is not a Business Day will be made on the next Business Day as if made on the date that the payment was due and no interest will accrue on that payment for the period from the original payment date to the date of that payment on the next Business Day.

We will pay principal and interest on the notes, register the transfer of the notes and exchange the notes at our office or agency maintained for that purpose, which initially will be the Corporate Trust Office of the trustee. We may change the paying agent or registrar without prior notice to the holders of the notes, and we or any of

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our subsidiaries may act as paying agent or registrar. So long as the notes are represented by global debt securities, the interest payable on the notes will be paid to Cede & Co., the nominee of the depositary, or its registered assigns as the registered owner of such global debt securities, by wire transfer of immediately available funds on each of the applicable interest payment dates. If any of the notes are no longer represented by a global debt security, we have the option to pay interest by check mailed to the address of the person entitled to the interest. No service charge will be made for any transfer or exchange of notes, but we may require payment of a sum sufficient to cover any tax or other governmental charge payable.

The notes are our senior unsecured obligations and rank equally in right of payment with all our existing and future senior unsecured debt. The notes are effectively junior to all of our secured indebtedness to the extent of the assets securing such indebtedness. Our operations are conducted through our subsidiaries and, therefore, we depend on the cash flow of our subsidiaries to meet our obligations, including our obligations under the notes. Our subsidiaries are not guarantors of the notes. Accordingly, the notes are effectively subordinated to all indebtedness and other obligations of our subsidiaries. See “Risk Factors—Our holding company structure results in structural subordination of the notes and may affect our ability to make payments on the notes.”

As of December 31, 2018, after giving effect to the transactions described under “Capitalization,” we and our subsidiaries would have had total outstanding consolidated debt of approximately $         billion, consisting of:

As of December 31, 2018, after giving effect to the transactions described under “Capitalization,” we had the ability to borrow an additional $         billion under the 2013 Credit Facility and the 2014 Credit Facility, net of approximately $10.0 million of outstanding undrawn letters of credit.

As of the issue date, our current subsidiaries, other than those listed in the definition of “Unrestricted Subsidiary” under “— Certain Definitions” below, will be Subsidiaries. Under certain circumstances, we will be able to designate current or future subsidiaries as Unrestricted Subsidiaries. Unrestricted Subsidiaries will not be subject to the restrictive covenants set forth in the indenture.

The notes are not subject to a sinking fund.

Transfer and Exchange

A holder may transfer or exchange notes in accordance with the indenture. The registrar and the trustee may require a holder, among other things, to furnish appropriate endorsements and transfer documents in connection with a transfer of notes. Holders will be required to pay all taxes due on transfer. We are not required to transfer or exchange any note selected for redemption or tendered for repurchase. Also, we are not required to transfer or exchange any note for a period of 15 days preceding the first mailing of notice of redemption of notes to be redeemed.

Optional Redemption

The 2024 notes are redeemable at our election, in whole or in part, at any time and from time to time. If we redeem the 2024 notes prior to April 15, 2024 (one month prior to their maturity date), we will pay a redemption price equal to the greater of:

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plus, in either of the above cases, accrued and unpaid interest to the date of redemption on the 2024 notes to be redeemed.

If we redeem the 2024 notes on or after April 15, 2024 (one month prior to their maturity date), we will pay a redemption price equal to 100% of the principal amount of the 2024 notes to be redeemed plus accrued interest to the redemption date.

The 2029 notes are redeemable at our election, in whole or in part, at any time and from time to time. If we redeem the 2029 notes prior to December 15, 2028 (three months prior to their maturity date), we will pay a redemption price equal to the greater of:

plus, in either of the above cases, accrued and unpaid interest to the date of redemption on the 2029 notes to be redeemed.

If we redeem the 2029 notes on or after December 15, 2028 (three months prior to their maturity date), we will pay a redemption price equal to 100% of the principal amount of the notes to be redeemed plus accrued interest to the redemption date.

If the optional redemption date is on or after an interest record date and on or before the related interest payment date, the accrued and unpaid interest, if any, will be paid to the person in whose name the note is registered at the close of business on such record date.

We will mail or cause to be mailed a notice of redemption at least 30 days but not more than 60 days before the redemption date to each holder of the notes to be redeemed at their registered address, except that redemption notices may be mailed more than 60 days prior to a redemption date if the notice is issued in connection with a defeasance of the notes or a satisfaction and discharge of the indenture. Notices of redemption may not be conditional.

Unless we default in payment of the redemption price, on and after the redemption date, interest will cease to accrue on the notes or portions thereof called for redemption. Notes called for redemption become due on the date fixed for redemption.

If less than all of the notes are to be redeemed, the trustee will select notes for redemption as follows:

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However, no note of $2,000 in principal amount or less shall be redeemed in part. If any note is to be redeemed in part only, the notice of redemption relating to such note will state the portion of the principal amount to be redeemed. A new note in principal amount equal to the unredeemed portion will be issued in the name of the holder thereof upon cancellation of the original note.

Repurchase of Notes Upon a Change of Control Triggering Event

If a Change of Control Triggering Event occurs with respect to the notes, each holder of notes will have the right to require us to repurchase all or any part, equal to $2,000 or an integral multiple of $1,000 thereafter, of that holder’s notes, provided that any unpurchased portion of the notes will equal $2,000 or an integral multiple of $1,000 thereafter, pursuant to a Change of Control Offer on the terms set forth in the indenture. In the Change of Control Offer, we will offer a Change of Control Payment in cash equal to 101% of the aggregate principal amount of notes repurchased plus accrued and unpaid interest on the notes up to but excluding the date of repurchase. Within 30 days following any Change of Control Triggering Event, if we had not, prior to the Change of Control Triggering Event, sent a redemption notice for all the notes in connection with an optional redemption permitted by the indenture, we will mail or cause to be mailed a notice to each registered holder briefly describing the transaction or transactions that constitute a Change of Control Triggering Event and offering to repurchase notes on the date specified in such notice (the “Change of Control Payment Date”), which date will be no earlier than 30 days and no later than 60 days from the date the notice is mailed, pursuant to the procedures required by the indenture and described in such notice.

We will comply with the requirements of Rule 14e-1 under the Exchange Act, and any other securities laws and regulations thereunder to the extent such laws and regulations are applicable to any Change of Control Offer. To the extent that the provisions of any securities laws or regulations conflict with the provisions of the indenture relating to the covenant described above, we will comply with the applicable securities laws and regulations and will not be deemed to have breached our obligations under the provisions of the indenture relating to the covenant described above by virtue of such conflict.

On the Change of Control Payment Date, we will, to the extent lawful:

(1) accept for payment all notes or portions thereof properly tendered pursuant to the Change of Control Offer;

(2) deposit with the paying agent an amount equal to the Change of Control Payment in respect of all notes or portions thereof properly tendered; and

(3) deliver or cause to be delivered to the trustee the notes so accepted together with an Officers’ Certificate stating the aggregate principal amount of notes or portions thereof being purchased by us.

The paying agent will promptly mail to each registered holder of notes so tendered the Change of Control Payment for such notes, and the trustee will promptly authenticate and mail, or cause to be transferred by book entry, to each holder a new note equal in principal amount to any unpurchased portion of the notes surrendered, if any; provided that each such new note will be in a principal amount of $2,000 or an integral multiple of $1,000 thereafter. Any note so accepted for payment will cease to accrue interest on and after the Change of Control Payment Date.

Except as described above, the provisions described above will be applicable regardless of whether or not any other provisions of the indenture are applicable. Other than with respect to a Change of Control Triggering Event, the indenture does not contain provisions that permit the holders of the notes to require that we repurchase or redeem the notes in the event of a takeover, recapitalization or similar transaction.

Holders will not be entitled to require us to purchase their notes in the event of a takeover, recapitalization, leveraged buyout or similar transaction that is not a Change of Control. We may nonetheless incur significant additional indebtedness in connection with such a transaction.

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For the avoidance of doubt, a Change of Control will not be deemed to have occurred if we merge with an affiliate solely for the purpose of reincorporating American Tower in its current or another jurisdiction within the United States of America.

Holders may not be able to require us to purchase their notes in certain circumstances involving a significant change in the composition of our board of directors, including a proxy contest where our board of directors does not endorse the dissident slate of directors but approves them as Continuing Directors. In this regard, a decision of the Delaware Chancery Court (not involving us or our securities) considered a change of control redemption provision of an indenture governing publicly traded debt securities that is substantially similar to the change of control event described in clause (3) of the definition of “Change of Control.” In its decision, the court noted that a board of directors may “approve” a dissident shareholder’s nominees solely for purposes of such an indenture, provided the board of directors determines in good faith that the election of the dissident nominees would not be materially adverse to the interests of the corporation or its stockholders (without taking into consideration the interests of the holders of debt securities in making this determination). See “Risk Factors—We may be unable to repay the notes when due or repurchase the notes when we are required to do so and holders may be unable to require us to repurchase their notes in certain circumstances.”

We will not be required to make a Change of Control Offer upon a Change of Control Triggering Event if a third party makes the Change of Control Offer in the manner, at the times and otherwise in compliance with the requirements set forth in the indenture applicable to a Change of Control Offer made by us and purchases all notes properly tendered and not withdrawn under the Change of Control Offer.

A Change of Control Offer may be made in advance of a Change of Control Triggering Event, and conditional upon the occurrence of such Change of Control Triggering Event, if a definitive agreement is in place for the Change of Control Triggering Event at the time of making the Change of Control Offer.

There can be no assurance that we will have sufficient funds available at the time of any Change of Control Triggering Event, and consummate a Change of Control Offer for all notes then outstanding, at a purchase price for 101% of their principal amount, plus accrued and unpaid interest to the Change of Control Payment Date. The indentures for our other outstanding indebtedness also provide for repurchase rights upon a change in control and, in some cases, certain other events under different terms. As a result, holders of our other indebtedness may have the ability to require us to repurchase their debt securities before the holders of the notes offered hereby would have such repurchase rights. In addition, a Change of Control (as described herein) and certain other change of control events may constitute an event of default under the 2013 Credit Facility and the 2014 Credit Facility. As a result, we may not be able to make any of the required payments on, or repurchases of, the notes without obtaining the consent of the lenders under the 2013 Credit Facility or the 2014 Credit Facility with respect to such payment or repurchase.

Covenants

Limitations on liens

Under the indenture, we will not, and will not permit any of our Subsidiaries to, allow any Lien (other than Permitted Liens) on any of our or our Subsidiaries’ property or assets (which includes Capital Stock) securing Indebtedness, unless the Lien secures the notes equally and ratably with, or prior to, any other Indebtedness secured by such Lien, so long as such other Indebtedness is so secured.

Notwithstanding the foregoing, we may, and may permit any of our Subsidiaries to, incur Liens securing Indebtedness without equally and ratably securing the notes if, after giving effect to the incurrence of such Liens, the aggregate amount (without duplication) of the Indebtedness secured by Liens (other than Permitted Liens) on the property or assets (which includes Capital Stock) of us and our Subsidiaries shall not exceed the Permitted Amount at the time of the incurrence of such Liens (it being understood that Liens securing the SpectraSite ABS Facility shall be deemed to be incurred pursuant to this paragraph).

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Trustee

The trustee for the notes is U.S. Bank National Association, and we have initially appointed the trustee as the paying agent, registrar and custodian with regard to the notes. Except during the continuance of an Event of Default, the trustee will perform only such duties as are specifically set forth in the indenture. During the existence of an Event of Default, the trustee will exercise such of the rights and powers vested in it under the indenture and use the same degree of care and skill in its exercise as a prudent person would exercise under the circumstances in the conduct of such person’s own affairs. The holders of a majority in principal amount of the then outstanding notes will have the right to direct the time, method and place of conducting any proceeding for exercising any remedy available to the trustee, subject to certain exceptions. Subject to these provisions, the trustee will be under no obligation to exercise any of its rights or powers under the indenture at the request of any holder of notes, unless such holder has offered to the trustee security and indemnity satisfactory to it against any loss, liability or expense.

Pursuant and subject to the Trust Indenture Act, the trustee will be permitted to engage in other transactions with us; however, if the trustee acquires any conflicting interest (as defined in the Trust Indenture Act), it would be required to eliminate such conflict within 90 days, apply to the SEC for permission to continue as trustee or resign. The trustee is also the trustee under the trust and servicing agreement related to our securitization transaction.

Governing Law

The indenture and the notes will be governed by and construed in accordance with the laws of the State of New York.

Book-Entry; Delivery and Form

We have obtained the information in this section concerning DTC, Clearstream and Euroclear and their book-entry systems and procedures from sources that we believe to be reliable. We take no responsibility for an accurate portrayal of this information. In addition, the description of the clearing systems in this section reflects our understanding of the rules and procedures of DTC, Clearstream and Euroclear as they are currently in effect. Those systems could change their rules and procedures at any time.

The notes will initially be represented by one or more fully registered global notes. Each such global note will be deposited with, or on behalf of, DTC or any successor thereto and registered in the name of Cede & Co. (DTC’s nominee). You may hold your interests in the global notes in the United States through DTC, or in Europe through Clearstream or Euroclear, either as a participant in such systems or indirectly through organizations that are participants in such systems. Clearstream and Euroclear will hold interests in the global notes on behalf of their respective participating organizations or customers through customers’ securities accounts in Clearstream’s or Euroclear’s names on the books of their respective depositaries, which in turn will hold those positions in customers’ securities accounts in the depositaries’ names on the books of DTC. Citibank, N.A. will act as depositary for Clearstream and the Euroclear Operator will act as depositary for Euroclear.

So long as DTC or its nominee is the registered owner of the global securities representing the notes, DTC or such nominee will be considered the sole owner and holder of the notes for all purposes of the notes and the indenture. Except as provided below, owners of beneficial interests in the notes will not be entitled to have the notes registered in their names, will not receive or be entitled to receive physical delivery of the notes in definitive form and will not be considered the owners or holders of the notes under the indenture, including for purposes of receiving any reports delivered by us or the trustee pursuant to the indenture. Accordingly, each person owning a beneficial interest in a note must rely on the procedures of DTC or its nominee and, if such person is not a participant, on the procedures of the participant through which such person owns its interest, in order to exercise any rights of a holder of notes.

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Unless and until we issue the notes in fully certificated, registered form under the limited circumstances described below under the heading “— Certificated Notes”:

The Depository Trust Company

DTC will act as securities depositary for the notes. The notes will be issued as fully registered notes registered in the name of Cede & Co. DTC is:

DTC holds securities that its direct participants deposit with DTC. DTC facilitates the settlement among direct participants of securities transactions, such as transfers and pledges, in deposited securities through electronic computerized book-entry changes in direct participants’ accounts, thereby eliminating the need for physical movement of securities certificates.

Direct participants of DTC include securities brokers and dealers (including the underwriters), banks, trust companies, clearing corporations and certain other organizations. DTC is owned by a number of its direct participants. Indirect participants of DTC, such as securities brokers and dealers, banks and trust companies, can also access the DTC system if they maintain a custodial relationship with a direct participant.

Purchases of notes under DTC’s system must be made by or through direct participants, which will receive a credit for the notes on DTC’s records. The ownership interest of each beneficial owner is in turn to be recorded on the records of direct participants and indirect participants. Beneficial owners will not receive written confirmation from DTC of their purchase, but beneficial owners are expected to receive written confirmations providing details of the transaction, as well as periodic statements of their holdings, from the direct participants or indirect participants through which such beneficial owners entered into the transaction. Transfers of ownership interests in the notes are to be accomplished by entries made on the books of participants acting on behalf of beneficial owners. Beneficial owners will not receive certificates representing their ownership interests in notes, except as provided below under the heading “— Certificated Notes.”

To facilitate subsequent transfers, all notes deposited with DTC are registered in the name of DTC’s nominee, Cede & Co. The deposit of notes with DTC and their registration in the name of Cede & Co. effect no change in beneficial ownership. DTC has no knowledge of the actual beneficial owners of the notes. DTC’s records reflect only the identity of the direct participants to whose accounts such notes are credited, which may or may not be the beneficial owners. The participants will remain responsible for keeping account of their holdings on behalf of their customers.

Conveyance of notices and other communications by DTC to direct participants, by direct participants to indirect participants and by direct participants and indirect participants to beneficial owners will be governed by arrangements among them, subject to any statutory or regulatory requirements as may be in effect from time to time.

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Book-Entry Format

Under the book-entry format, the trustee will pay interest or principal payments to Cede & Co., as nominee of DTC. DTC will forward the payment to the direct participants, who will then forward the payment to the indirect participants (including Clearstream or Euroclear) or to you as the beneficial owner. You may experience some delay in receiving your payments under this system. Neither we, the trustee under the indenture nor any paying agent has any direct responsibility or liability for the payment of principal or interest on the notes to owners of beneficial interests in the notes.

DTC is required to make book-entry transfers on behalf of its direct participants and is required to receive and transmit payments of principal, premium, if any, and interest on the notes. Any direct participant or indirect participant with which you have an account is similarly required to make book-entry transfers and to receive and transmit payments with respect to the notes on your behalf. We and the trustee under the indenture have no responsibility for any aspect of the actions of DTC, Clearstream or Euroclear or any of their direct or indirect participants. In addition, we and the trustee under the indenture have no responsibility or liability for any aspect of the records kept by DTC, Clearstream, Euroclear or any of their direct or indirect participants relating to or payments made on account of beneficial ownership interests in the notes or for maintaining, supervising or reviewing any records relating to such beneficial ownership interests. We also do not supervise these systems in any way.

The trustee will not recognize you as a holder under the indenture, and you can only exercise the rights of a holder indirectly through DTC and its direct participants. DTC has advised us that it will only take action regarding a note if one or more of the direct participants to whom the note is credited directs DTC to take such action and only in respect of the portion of the aggregate principal amount of the notes as to which that participant or participants has or have given that direction. DTC can only act on behalf of its direct participants. Your ability to pledge notes to non-direct participants, and to take other actions, may be limited because you will not possess a physical certificate that represents your notes. Neither DTC nor Cede & Co. (nor any other DTC nominee) will consent or vote with respect to the notes unless authorized by a direct participant in accordance with DTC’s procedures. Under its usual procedures, DTC will mail an omnibus proxy to us as soon as possible after the record date. The omnibus proxy assigns Cede & Co.’s consenting or voting rights to those direct participants to whose accounts the notes are credited on the record date (identified in a listing attached to the omnibus proxy). Clearstream or Euroclear will credit payments to the cash accounts of Clearstream customers or Euroclear participants in accordance with the relevant system’s rules and procedures, to the extent received by its depositary. These payments will be subject to tax reporting in accordance with relevant United States tax laws and regulations. Clearstream or the Euroclear Operator, as the case may be, will take any other action permitted to be taken by a holder under the indenture on behalf of a Clearstream customer or Euroclear participant only in accordance with its relevant rules and procedures and subject to its depositary’s ability to effect those actions on its behalf through DTC.

Transfers Within and Among Book-Entry Systems

Transfers between DTC’s direct participants will occur in accordance with DTC rules. Transfers between Clearstream customers and Euroclear participants will occur in accordance with the applicable rules and operating procedures of Clearstream and Euroclear, respectively.

DTC will effect cross-market transfers between persons holding directly or indirectly through DTC, on the one hand, and directly or indirectly through Clearstream customers or Euroclear participants, on the other hand, in accordance with DTC rules on behalf of the relevant European international clearing system by its depositary. However, cross-market transactions will require delivery of instructions to the relevant European international clearing system by the counterparty in that system in accordance with its rules and procedures and within its established deadlines (European time). The relevant European international clearing system will, if the transaction meets its settlement requirements, instruct its depositary to effect final settlement on its behalf by delivering or receiving securities in DTC, and making or receiving payment in accordance with normal

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procedures for same-day funds settlement applicable to DTC. Clearstream customers and Euroclear participants may not deliver instructions directly to the depositaries.

Because of time-zone differences, credits of securities received in Clearstream or Euroclear resulting from a transaction with a DTC direct participant will be made during the subsequent securities settlement processing, dated the business day following the DTC settlement date. Those credits or any transactions in those securities settled during that processing will be reported to the relevant Clearstream customer or Euroclear participant on that business day. Cash received in Clearstream or Euroclear as a result of sales of securities by or through a Clearstream customer or a Euroclear participant to a DTC direct participant will be received with value on the DTC settlement date but will be available in the relevant Clearstream or Euroclear cash amount only as of the business day following settlement in DTC.

Although DTC, Clearstream and Euroclear have agreed to the foregoing procedures in order to facilitate transfers of notes among their respective participants, they are under no obligation to perform or continue to perform such procedures and such procedures may be discontinued at any time.

Certificated Notes

Unless and until they are exchanged, in whole or in part, for notes in definitive form in accordance with the terms of the notes, the notes may not be transferred except (1) as a whole by DTC to a nominee of DTC; (2) by a nominee of DTC to DTC or another nominee of DTC; or (3) by DTC or any such nominee to a successor of DTC or a nominee of such successor.

We will issue notes to you or your nominees, in fully certificated registered form, rather than to DTC or its nominees, only if:

If any of the four above events occurs, DTC is required to notify all direct participants that notes in fully certificated registered form are available through DTC. DTC will then surrender the global note representing the notes along with instructions for re-registration. The trustee will re-issue the notes in fully certificated registered form and will recognize the registered holders of the certificated notes as holders under the indenture.

Unless and until we issue the notes in fully certificated, registered form, (1) you will not be entitled to receive a certificate representing your interest in the notes; (2) all references in this prospectus supplement to actions by holders will refer to actions taken by the depositary upon instructions from their direct participants; and (3) all references in this prospectus supplement to payments and notices to holders will refer to payments and notices to the depositary, as the registered holder of the notes, for distribution to you in accordance with its policies and procedures.

Certain Definitions

“Adjusted EBITDA” means, for the 12-month period preceding the calculation date, for us and our Subsidiaries on a consolidated basis in accordance with GAAP, the sum of (a) Net Income, plus (b) to the extent

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deducted in determining Net Income, the sum of (i) Interest Expense, (ii) income tax expense, including, without limitation, taxes paid or accrued based on income, profits or capital, including state, franchise and similar taxes and foreign withholding taxes, (iii) depreciation and amortization (including, without limitation, amortization of goodwill and other intangible assets), (iv) extraordinary losses and non-recurring non-cash charges and expenses, (v) all other non-cash charges, expenses and interest (including, without limitation, any non-cash losses in respect of Commodity Agreements, Currency Agreements or Interest Rate Agreements, non-cash impairment charges, non-cash valuation charges for stock option grants or vesting of restricted stock awards or any other non-cash compensation charges, and losses from the early extinguishment of Indebtedness) and (vi) nonrecurring charges and expenses, restructuring charges, transaction expenses (including, without limitation, transaction expenses incurred in connection with any merger or acquisition) and underwriters’ fees or discounts, and severance and retention payments in connection with any merger or acquisition, in each case for such period, less extraordinary gains and cash payments (not otherwise deducted in determining net income) made during such period with respect to non-cash charges that were added back in a prior period; provided, however, (I) with respect to any Person that became a Subsidiary, or was merged with or consolidated into us or any Subsidiary, during such period, or any acquisition by us or any Subsidiary of the assets of any Person during such period, “Adjusted EBITDA” shall, at our option in respect of any or all of the foregoing, also include the Adjusted EBITDA of such Person or attributable to such assets, as applicable, during such period as if such acquisition, merger or consolidation had occurred on the first day of such period and (II) with respect to any Person that has ceased to be a Subsidiary during such period, or any material assets of us or any Subsidiary sold or otherwise disposed of by us or any Subsidiary during such period, “Adjusted EBITDA” shall exclude the Adjusted EBITDA of such Person or attributable to such assets, as applicable, during such period as if such sale or disposition of such Subsidiary or such assets had occurred on the first day of such period.

“Adjusted Treasury Rate” means, with respect to any redemption date:

The Adjusted Treasury Rate shall be calculated on the third Business Day preceding the redemption date.

“Beneficial Owner” has the meaning assigned to such term in Rule 13d-3 and Rule 13d-5 under the Exchange Act, except that in calculating the beneficial ownership of any particular “person” as such term is used in Section 13(d)(3) of the Exchange Act, such “person” will be deemed to have beneficial ownership of all securities that such “person” has the right to acquire by conversion or exercise of other securities, whether such right is currently exercisable or is exercisable only upon the occurrence of a subsequent condition.

“Board of Directors” means either our Board of Directors or any committee of such Board duly authorized to act on our behalf.

“Board Resolution” means one or more resolutions duly adopted or consented to by the Board of Directors and in full force and effect.

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“Business Day” means any day except a Saturday, Sunday or other day on which commercial banks in the City of New York are authorized or obligated by law or executive order to close.

“Capital Lease Obligations” means, at the time any determination is to be made, the amount of the liability in respect of a capital lease that would at that time be required to be capitalized on a balance sheet in accordance with GAAP.

“Capital Stock” means:

“Change of Control” means the occurrence of any of the following:

“Change of Control Triggering Event” means the occurrence of both a Change of Control and a Ratings Decline.

“Commodity Agreement” of any Person means any commodity forward contract, commodity swap agreement, commodity option agreement or other similar agreement or arrangement to which such Person is a party.

“Comparable Treasury Issue” means the United States Treasury security selected by an Independent Investment Banker as having a maturity comparable to the remaining term of the notes, calculated as if the maturity date of such notes were the applicable First Par Call Date (the “Remaining Life”), that would be utilized, at the time of selection and in accordance with customary financial practice, in pricing new issues of corporate debt securities of comparable maturity to the Remaining Life of such notes.

“Comparable Treasury Price” means, for any redemption date, (1) the average of four Reference Treasury Dealer Quotations for such redemption date, after excluding the highest and lowest Reference Treasury Dealer Quotations, or (2) if the Independent Investment Banker obtains fewer than four such Reference Treasury Dealer Quotations the average of all such quotations.

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“Continuing Director” means, as of any date of determination, any member of our Board of Directors who:

“Corporate Trust Office” means the designated office of the trustee at which at any time its corporate trust business shall be administered, which office at the date hereof is located at One Federal Street, 3^rd Floor, EX-MA-FED, Boston, MA 02110, Attention: David W. Doucette, Vice President, or such other address as the trustee may designate from time to time by notice to the holders of the notes and us, or the principal corporate trust office of any successor trustee (or such other address as such successor trustee may designate from time to time by notice to the holders of the notes and us).

“Currency Agreement” of any Person means any foreign exchange contract, currency swap agreement or other similar agreement or arrangement as to which such Person is a party.

“Disqualified Stock” means any Capital Stock that, by its terms (or by the terms of any security into which it is convertible, or for which it is exchangeable, in each case at the option of the holder of the Capital Stock), or upon the happening of any event, matures or is mandatorily redeemable, pursuant to a sinking fund obligation or otherwise, or redeemable at the option of the holder of the Capital Stock, in whole or in part, on or prior to the Stated Maturity of the notes.

“DTC” means The Depository Trust Company.

“Fair Market Value” means, with respect to any asset, the price that (after taking into account any liabilities relating to such asset) would be paid in an arm’s-length transaction between an informed and willing seller under no compulsion to sell and an informed and willing buyer under no compulsion to buy, as determined in good faith by the Board of Directors, whose determination shall be conclusive if evidenced by a Board Resolution.

“First Par Call Date” means, with respect to the 2024 notes, April 15, 2024 and, with respect to the 2029 notes, December 15, 2028.

“Fitch” means Fitch, Inc. or any successor to the rating agency business thereof.

“Foreign Subsidiary” means, with respect to any Person, (a) any Subsidiary of such Person that is not organized or existing under the laws of, and whose principal business is conducted outside of, the United States, any state thereof, the District of Columbia, or any territory thereof (for purposes of this definition only, the “United States”), or (b) any Subsidiary of such Person that is organized or existing under the laws of the United States whose only material assets are the Capital Stock of Foreign Subsidiaries meeting clause (a) of this definition.

“GAAP” means generally accepted accounting principles set forth in the standards, statements and pronouncements of the Financial Accounting Standards Board, or in such other statements by such other entity as may be approved by a significant segment of the accounting profession of the United States, which are in effect on the Issue Date, provided however, that leases shall continue to be classified and accounted for on a basis consistent with that reflected in the financial statements of the Company for the fiscal year ended December 31, 2018 for all purposes, not withstanding any change in GAAP relating thereto, including with respect to Accounting Standards Codification 842.

“Guarantee” means a guarantee (other than by endorsement of negotiable instruments for collection in the ordinary course of business), direct or indirect, in any manner (including, without limitation, by way of a pledge of assets or through letters of credit or reimbursement agreements in respect thereof), of all or any part of any Indebtedness. The term “Guarantee” used as a verb has a corresponding meaning.

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“Indebtedness” means, with respect to any Person, any indebtedness of such Person, whether or not contingent:

if and to the extent any of the preceding items (other than letters of credit and obligations under Interest Rate Agreements, Commodity Agreements and Currency Agreements) would appear as a liability upon a balance sheet of such Person prepared in accordance with GAAP. In addition, the term “Indebtedness” includes all Indebtedness of others secured by a Lien on any asset of such Person whether or not such Indebtedness is assumed by such Person (the amount of such Indebtedness as of any date being deemed to be the lesser of the Fair Market Value of such property or assets as of such date or the principal amount of such Indebtedness of such other Person so secured) and, to the extent not otherwise included, the Guarantee by such Person of any Indebtedness of any other Person.

The amount of any Indebtedness outstanding as of any date shall be:

“Independent Investment Banker” means one of the Reference Treasury Dealers appointed by us.

“Interest Expense” means, for any period, all cash interest expense (including imputed interest with respect to Capital Lease Obligations and commitment fees) with respect to any of our Indebtedness and our Subsidiaries’ Indebtedness on a consolidated basis during such period pursuant to the terms of such Indebtedness.

“Interest Rate Agreement” of any Person means any interest rate protection agreement, interest rate future agreement, interest rate option agreement, interest rate swap agreement, interest rate cap agreement, interest rate collar agreement, interest rate hedge agreement, option or future contract or other similar agreement or arrangement as to which such Person is a party.

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“Investment Grade Rating” means a rating equal to or greater than BBB- by S&P and Fitch and Baa3 by Moody’s or the equivalent thereof under any new ratings system if the ratings system of any such agency shall be modified after the Issue Date, or the equivalent rating or any other Ratings Agency selected by us as provided in the definition of Ratings Agency.

“Issue Date” means March     , 2019.

“Licenses” means, collectively, any telephone, microwave, radio transmissions, personal communications or other license, authorization, certificate of compliance, franchise, approval or permit, whether for the construction, ownership or operation of any communications tower facilities, granted or issued by the Federal Communications Commission (or other similar or successor agency of the federal government administering the Communications Act of 1934 or any similar or successor federal statute) and held by us or any of our Subsidiaries.

“Lien” means, with respect to any property or assets, including Capital Stock, any mortgage, lien, pledge, charge, security interest or encumbrance of any kind in respect of such asset, whether or not filed, recorded or otherwise perfected under applicable law (including any conditional sale or other title retention agreement, any lease in the nature thereof, any option or other agreement to sell or give a security interest in and any filing of or agreement to give any financing statement under the Uniform Commercial Code (or equivalent statutes) of any jurisdiction).

“Moody’s” means Moody’s Investors Services, Inc. or any successor to the rating agency business thereof.

“Net Income” means, for any period of determination, net income (loss) of us and our Subsidiaries, on a consolidated basis, determined in accordance with GAAP.

“Newly Created Subsidiary” means a newly created direct or indirect Subsidiary of us that is formed or organized after the Issue Date; provided that neither we nor any of our Subsidiaries shall have transferred, or may in the future transfer, any assets (other than cash or cash equivalents) to such Newly Created Subsidiary for so long as such Newly Created Subsidiary remains designated as an Unrestricted Subsidiary.

“Officers’ Certificate” means, with respect to any Person, a certificate signed by the chairman of the Board of Directors, the chief executive officer, the president, the chief operating officer, the chief financial officer, or any vice president and by the treasurer, any assistant treasurer, the controller, any assistant controller, the secretary or any assistant secretary of such Person in accordance with the applicable provisions of the indenture.

“Permitted Amount” means, on any date, an amount equal to 3.5 times Adjusted EBITDA as of the most recent fiscal quarter for which our financial statements are internally available immediately preceding such date.

“Permitted Liens” means:

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“Person” means any individual, corporation, limited liability company, partnership, joint venture, association, joint stock company, trust, estate, unincorporated organization or government or any agency or political subdivision thereof or any other entity.

“Ratings Agencies” means (1) S&P, Moody’s and Fitch; and (2) if any of S&P, Moody’s and Fitch ceases to rate the notes or ceases to make a rating on the notes publicly available, an entity registered as a “nationally

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recognized statistical rating organization” (registered as such pursuant to Rule 17g-1 of the Exchange Act) then making a rating on the notes publicly available selected by us (as certified by an Officers’ Certificate), which shall be substituted for S&P, Moody’s or Fitch, as the case may be.

“Ratings Decline” means the occurrence of the following on, or within 90 days after, the date of the public notice of the occurrence of a Change of Control or of the intention by us or any third party to effect a Change of Control (which period shall be extended for so long as the rating of the notes is under publicly announced consideration for possible downgrade by any of the Ratings Agencies if such period exceeds 90 days): (1) in the event that the notes have an Investment Grade Rating by all three Ratings Agencies, the notes cease to have an Investment Grade Rating by two of the three Rating Agencies, (2) in the event that the notes have an Investment Grade Rating by only two Ratings Agencies, the notes cease to have an Investment Grade Rating by both such Rating Agencies, or (3) in the event that the notes do not have an Investment Grade Rating, the rating of the notes by two of the three Ratings Agencies (or, if there are less than three Rating Agencies rating the notes, the rating of each Rating Agency) decreases by one or more gradations (including gradations within ratings categories as well as between rating categories) or is withdrawn.

“Reference Treasury Dealer” means any of the primary U.S. Government securities dealers in New York City.

“Reference Treasury Dealer Quotations” means, with respect to each Reference Treasury Dealer and any redemption date, the average, as determined by the Independent Investment Banker, of the bid and asked prices for the Comparable Treasury Issue (expressed in each case as a percentage of its principal amount) quoted in writing to the Independent Investment Banker at 5:00 p.m., New York City time, on the third Business Day preceding such redemption date.

“S&P” means Standard & Poor’s Rating Services, a division of S&P Global Inc., or any successor to the rating agency business thereof.

“SpectraSite ABS Facility” means that certain mortgage loan more fully described in the Offering Memorandum dated March 27, 2018 regarding the $1,800.0 million Secured Tower Revenue Securities, Series 2018-1A and 2013-2A.

“Stated Maturity” means, (1) with respect to any debt security, the date specified in such debt security as the fixed date on which the final installment of principal of such debt security is due and payable and (2) with respect to any scheduled installment of principal of or interest on any debt security, the date specified in such debt security as the fixed date on which such installment is due and payable.

“Subsidiary” means, with respect to any Person, (1) any corporation, limited liability company, association or other business entity of which more than 50% of the voting power of the outstanding Voting Stock is owned, directly or indirectly, by such Person and one or more other Subsidiaries of such Person or (2) any partnership (A) the sole general partner or the managing general partner of which is such Person or a Subsidiary of such Person or (B) the only general partners of which are such Person or one or more Subsidiaries of such Person (or any combination thereof). The term “Subsidiary” with respect to us shall not include any Unrestricted Subsidiary.

“Unrestricted Subsidiary” means (a) any Foreign Subsidiary or Newly Created Subsidiary of us that is designated by the Board of Directors as an Unrestricted Subsidiary until such time as the Board of Directors may designate it to be a Subsidiary, provided that no Default or Event of Default would occur or be existing following such designation, and (b) any subsidiary of an Unrestricted Subsidiary. Any such designation by the Board of Directors shall be evidenced to the trustee by filing a Board Resolution with the trustee giving effect to such designation. At the time of designation of an Unrestricted Subsidiary as a Subsidiary, such Subsidiary shall be deemed to incur outstanding Indebtedness and grant any existing Liens.

“Voting Stock” of any Person as of any date means the Capital Stock of such Person that is normally entitled to vote in the election of the board of directors, managers or trustees of such Person.

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MATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS

Tax legislation enacted in December 2017 made substantial changes to the Internal Revenue Code of 1986, as amended (the “Code”). Among those changes are a significant permanent reduction in the generally applicable corporate income tax rate, changes in the taxation of international income, changes in the taxation of individuals and other noncorporate taxpayers that generally reduce their taxes on a temporary basis subject to “sunset” provisions and the elimination or modification of various deductions (including substantial limitation of the deduction for personal state and local taxes imposed on individuals and limitations on the deduction of business interest expense and net operating losses). While the effect of these and other changes made in this legislation is still uncertain in many respects, and many of the provisions of the new law will require additional guidance in order to assess their effect, we do not anticipate that the new legislation will materially impact our qualification and taxation as a REIT.

Investors in the notes should consider the information in the accompanying prospectus under “Material U.S. Federal Income Tax Considerations Relevant to Holders of Our Debt Securities”, which should be applied separately to each series of notes.

Withholding under sections 1471 through 1474 of the Code (“FATCA”) is discussed generally under the heading “Material U.S. Federal Income Tax Considerations Relevant to Holders of Our Debt Securities—Information Reporting, Backup Withholding and Foreign Account Withholding” of the accompanying prospectus. Pursuant to recently issued proposed Treasury regulations, which holders may rely on, FATCA withholding generally will apply to payments of interest on the notes, but will not apply to payments of gross proceeds from a sale, repayment, retirement, or other disposition of notes.

In addition, the following should be appended to the prospectus after the heading “Tax Consequences to U.S. Holders.”

Under recently enacted legislation, U.S. Holders that use an accrual method of accounting for tax purposes generally will be required to include certain amounts in income no later than the time such amounts are reflected on certain audited financial statements. The application of this rule thus may require the accrual of income earlier than would be the case under the general tax rules described below, although the precise application of this rule is unclear at this time. U.S. Holders that use an accrual method of accounting should consult with their tax advisors regarding the potential applicability of this legislation to their particular situation.

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UNDERWRITING

Barclays Capital Inc., Mizuho Securities USA LLC, RBC Capital Markets, LLC, SG Americas Securities, LLC and TD Securities (USA) LLC are acting as joint book-running managers of the offering and as representatives of the underwriters named below. Subject to the terms and conditions stated in the underwriting agreement dated the date of this prospectus supplement, each underwriter named below has severally agreed to purchase, and we have agreed to sell to that underwriter, the principal amount of notes set forth opposite the underwriter’s name.

The underwriting agreement provides that the obligations of the underwriters to purchase the notes included in this offering are subject to approval of legal matters by counsel and to other conditions. The underwriters are obligated to purchase all the notes if they purchase any of the notes.

Notes sold by the underwriters to the public will initially be offered at the initial public offering prices set forth on the cover of this prospectus supplement. Any 2024 notes sold by the underwriters to securities dealers may be sold at a selling concession from the initial public offering price not in excess of     % of the principal amount of the 2024 notes. Any 2029 notes sold by the underwriters to securities dealers may be sold at a selling concession from the initial public offering price not in excess of     % of the principal amount of the 2029 notes. Any such securities dealers may resell any 2024 notes purchased from the underwriters to certain other brokers or dealers at a discount from the initial public offering price not in excess of     % of the principal amount of the 2024 notes. Any such securities dealers may resell any 2029 notes purchased from the underwriters to certain other brokers or dealers at a discount from the initial public offering price not in excess of     % of the principal amount of the 2029 notes. If all the notes are not sold at the initial offering price, the underwriters may change the offering price and the other selling terms.

We expect that the delivery of the notes will be made against payment on March     , 2019, which is the third business day following the date of this prospectus supplement (this settlement cycle being referred to as “T+3”). Under Rule 15c6-1 of the Exchange Act, trades in the secondary market generally are required to settle in two business days, unless the parties to the trade expressly agree otherwise. Accordingly, purchasers who wish to trade the notes on the date of this prospectus supplement will be required, by virtue of the fact that the notes initially will settle in T+3, to specify an alternate settlement cycle at the time of any such trade to prevent a failed settlement and should consult their own advisors.

The following table shows the underwriting discounts and commissions that we are to pay to the underwriters in connection with this offering (expressed as a percentage of the principal amount of the notes).

We estimate that our total expenses for this offering will be $         million. We have entered into an agreement with the underwriters regarding a reimbursement of $         million of our offering expenses.

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In connection with the offering, the underwriters (or persons acting on their behalf) may purchase and sell notes in the open market. Purchases and sales in the open market may include short sales, purchases to cover short positions, stabilizing purchases and penalty bids.