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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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 E90MZLW3DBEDv3VMriVWiA==

<SEC-DOCUMENT>0000757011-04-000027.txt : 20040702
<SEC-HEADER>0000757011-04-000027.hdr.sgml : 20040702
<ACCEPTANCE-DATETIME>20040702120814
ACCESSION NUMBER:		0000757011-04-000027
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20040701
FILED AS OF DATE:		20040702

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			USG CORP
		CENTRAL INDEX KEY:			0000757011
		STANDARD INDUSTRIAL CLASSIFICATION:	CONCRETE GYPSUM  PLASTER PRODUCTS [3270]
		IRS NUMBER:				363329400
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		125 S FRANKLIN ST
		STREET 2:		DEPT. 188
		CITY:			CHICAGO
		STATE:			IL
		ZIP:			60606
		BUSINESS PHONE:		3126064000

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BROWN KEITH A
		CENTRAL INDEX KEY:			0001205514

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-08864
		FILM NUMBER:		04898240

	BUSINESS ADDRESS:	
		STREET 1:		1293 S MAIN ST
		CITY:			AKRON
		STATE:			OH
		ZIP:			44301
		BUSINESS PHONE:		3307616369

	MAIL ADDRESS:	
		STREET 1:		1293 S MAIN ST
		CITY:			ARKON
		STATE:			OH
		ZIP:			44301
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-07-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000757011</issuerCik>
        <issuerName>USG CORP</issuerName>
        <issuerTradingSymbol>usg</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001205514</rptOwnerCik>
            <rptOwnerName>BROWN KEITH A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1293 S MAIN ST</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>ARKON</rptOwnerCity>
            <rptOwnerState>OH</rptOwnerState>
            <rptOwnerZipCode>44301</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common stock.</value>
            </securityTitle>
            <transactionDate>
                <value>2004-07-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>500</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4608</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Annual equity grant under the USG Corporation Stock Compensation Program for Non-Employee Directors.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Robert J. Burrell, Attorney-In-Fact</signatureName>
        <signatureDate>2004-07-01</signatureDate>
    </ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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