<SEC-DOCUMENT>0001051470-17-000054.txt : 20170221
<SEC-HEADER>0001051470-17-000054.hdr.sgml : 20170221
<ACCEPTANCE-DATETIME>20170221194052
ACCESSION NUMBER:		0001051470-17-000054
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20170216
FILED AS OF DATE:		20170221
DATE AS OF CHANGE:		20170221

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CROWN CASTLE INTERNATIONAL CORP
		CENTRAL INDEX KEY:			0001051470
		STANDARD INDUSTRIAL CLASSIFICATION:	REAL ESTATE INVESTMENT TRUSTS [6798]
		IRS NUMBER:				760470458
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		1220 AUGUSTA DRIVE
		STREET 2:		SUITE 600
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77057
		BUSINESS PHONE:		7135703000

	MAIL ADDRESS:	
		STREET 1:		1220 AUGUSTA DRIVE
		STREET 2:		SUITE 600
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77057

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Kavanagh Michael Joseph
		CENTRAL INDEX KEY:			0001691933

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-16441
		FILM NUMBER:		17626731

	MAIL ADDRESS:	
		STREET 1:		1220 AUGUSTA DRIVE SUITE 600
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77057
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_148772403869031.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-02-16</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001051470</issuerCik>
        <issuerName>CROWN CASTLE INTERNATIONAL CORP</issuerName>
        <issuerTradingSymbol>CCI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001691933</rptOwnerCik>
            <rptOwnerName>Kavanagh Michael Joseph</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1220 AUGUSTA DRIVE SUITE 600</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>HOUSTON</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>77057</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>SVP &amp; Chief Commercial Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Time RSUs</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2017-02-16</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>3867</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>3867.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3867</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Performance RSUs</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2017-02-16</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>13730</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
                <footnoteId id="F4"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>13730.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>13730</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Each Restricted Stock Unit (&quot;RSU&quot;) is issued pursuant to the Company's 2013 Long-Term Incentive Plan and represents a contingent right to receive one share of common stock, and vesting (i.e., forfeiture restriction termination) generally is subject to (i) the reporting person remaining an employee or director of the Company or its affiliates and (ii) the other criteria described in the footnotes below.</footnote>
        <footnote id="F2">33 1/3% of the Time RSUs vest on February 19 of each of 2018, 2019 and 2020.</footnote>
        <footnote id="F3">0% to 100% of the Performance RSUs may vest on February 19, 2020 based upon the Company's total stockholder return (&quot;TSR&quot;) performance rating (&quot;TSR Rank&quot;) relative to a peer group of companies approved by the Company's board of directors for the three year period ending February 16, 2020 (&quot;Period&quot;). If the TSR Rank is at the 30th percentile or more up to the 55th percentile, then 33.34% to 66.67% of the Performance RSUs vest on a pro rata basis based upon the level of the TSR Rank (i.e., approximately an additional 1.3336% of the units vest for each 1.0 percentile increase in the TSR Rank above the 30th percentile up to the 55th percentile), with 66.67% of the Performance RSUs vesting at the 55th percentile (Continued in Footnote 4)</footnote>
        <footnote id="F4">(Continued from Footnote 3) If the TSR Rank is at the 55th percentile or more, then 66.67% to 100% of the Performance RSUs vest on a pro rata basis based upon the level of the TSR Rank (i.e., approximately an additional 0.95229% of the units vest for each 1.0 percentile increase in the TSR Rank above the 55th percentile up to the 90th percentile (or above)), with 100% of the units vesting at or above the 90th percentile. However, if the TSR is negative for the Period and the TSR Rank is at or above the 30th percentile, the percentage of units which vest shall be 33.34%. If the TSR Rank is below the 30th percentile, 100% of the Performance RSUs will be forfeited.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Michael Joseph Kavanagh</signatureName>
        <signatureDate>2017-02-21</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
