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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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<SEC-DOCUMENT>0000100885-03-000016.txt : 20030609
<SEC-HEADER>0000100885-03-000016.hdr.sgml : 20030609
<ACCEPTANCE-DATETIME>20030609163950
ACCESSION NUMBER:		0000100885-03-000016
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030605
FILED AS OF DATE:		20030609

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			KORALESKI JOHN J
		CENTRAL INDEX KEY:			0001200010

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-06075
		FILM NUMBER:		03737707

	MAIL ADDRESS:	
		STREET 1:		UNION PACIFIC CORP
		STREET 2:		1416 DODGE ST
		CITY:			OMAHA
		STATE:			NE
		ZIP:			68179

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			UNION PACIFIC CORP
		CENTRAL INDEX KEY:			0000100885
		STANDARD INDUSTRIAL CLASSIFICATION:	RAILROADS, LINE-HAUL OPERATING [4011]
		IRS NUMBER:				132626465
		STATE OF INCORPORATION:			UT
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		1416 DODGE STREET
		STREET 2:		ROOM 830
		CITY:			OMAHA
		STATE:			NE
		ZIP:			68179
		BUSINESS PHONE:		402 271 5213

	MAIL ADDRESS:	
		STREET 1:		1416 DODGE STREET
		STREET 2:		ROOM 830
		CITY:			OMAHA
		STATE:			NE
		ZIP:			68179
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>

<ownershipDocument>

    <documentType>4</documentType>

    <periodOfReport>2003-06-05</periodOfReport>


    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000100885</issuerCik>
        <issuerName>UNION PACIFIC CORP</issuerName>
        <issuerTradingSymbol>UNP</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001200010</rptOwnerCik>
            <rptOwnerName>KORALESKI JOHN J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Exec. VP Marketing &amp; Sales</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeSecurity>
        <securityTitle>
            <value>Common Stock</value>
            <footnoteId id="F1"/>
        </securityTitle>
        <transactionDate>
            <value>2003-06-05</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>4</transactionFormType>
            <transactionCode>M</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
        </transactionCoding>
        <transactionTimeliness>
            <value></value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>6059</value>
            </transactionShares>
            <transactionValue>
                <value>42.87</value>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>A</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>129171</value>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>D</value>
            </directOrIndirectOwnership>
        </ownershipNature>
    </nonDerivativeSecurity>

    <nonDerivativeSecurity>
        <securityTitle>
            <value>Common Stock</value>
        </securityTitle>
        <transactionDate>
            <value>2003-06-05</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>4</transactionFormType>
            <transactionCode>F</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
        </transactionCoding>
        <transactionTimeliness>
            <value></value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>4238</value>
            </transactionShares>
            <transactionValue>
                <value>61.28</value>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>D</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>124933</value>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>D</value>
            </directOrIndirectOwnership>
        </ownershipNature>
    </nonDerivativeSecurity>

    <nonDerivativeSecurity>
        <securityTitle>
            <value>Common Stock</value>
        </securityTitle>
        <transactionDate>
            <value>2003-06-05</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>4</transactionFormType>
            <transactionCode>F</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
        </transactionCoding>
        <transactionTimeliness>
            <value></value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>828</value>
            </transactionShares>
            <transactionValue>
                <value>61.28</value>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>D</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>124105</value>
                <footnoteId id="F2"/>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>D</value>
            </directOrIndirectOwnership>
        </ownershipNature>
    </nonDerivativeSecurity>

    <derivativeSecurity>
        <securityTitle>
            <value>Non-Qualified Stock Option (right to buy)</value>
            <footnoteId id="F1"/>
        </securityTitle>
        <conversionOrExercisePrice>
            <value>42.87</value>
        </conversionOrExercisePrice>
        <transactionDate>
            <value>2003-06-05</value>
        </transactionDate>
        <transactionCoding>
            <transactionFormType>4</transactionFormType>
            <transactionCode>M</transactionCode>
            <equitySwapInvolved>0</equitySwapInvolved>
        </transactionCoding>
        <transactionTimeliness>
            <value></value>
        </transactionTimeliness>
        <transactionAmounts>
            <transactionShares>
                <value>6059</value>
            </transactionShares>
            <transactionValue>
                <value>0</value>
            </transactionValue>
            <transactionAcquiredDisposedCode>
                <value>D</value>
            </transactionAcquiredDisposedCode>
        </transactionAmounts>
        <exerciseDate>
            <value>1994-11-18</value>
        </exerciseDate>
        <expirationDate>
            <value>2003-11-18</value>
        </expirationDate>
        <underlyingSecurity>
            <underlyingSecurityTitle>
                <value>Common Stock</value>
            </underlyingSecurityTitle>
            <underlyingSecurityShares>
                <value>6059</value>
            </underlyingSecurityShares>
        </underlyingSecurity>
        <postTransactionAmounts>
            <sharesOwnedFollowingTransaction>
                <value>0</value>
            </sharesOwnedFollowingTransaction>
        </postTransactionAmounts>
        <ownershipNature>
            <directOrIndirectOwnership>
                <value>D</value>
            </directOrIndirectOwnership>
        </ownershipNature>
    </derivativeSecurity>

    <footnotes>
        <footnote id="F1">Number of shares and option price of outstanding options adjusted 10/16/96 to reflect new values following the spin-off of Union Pacific Resources Group, Inc.</footnote>
        <footnote id="F2">The reporting person also has the following indirect holdings: 1) 1,439.5147 units by a Managed Account which include holdings in Union Pacific's Payroll Based and Tax Reduction Stock Ownership Plans and 401(k) Plan as of the Transaction Date; and 2) 4,004 shares held in the Koraleski Family Limited Partnership, of which the reporting person and his wife are the sole general partners and the reporting person, his wife, and his children are the sole limited partners.  The reporting person disclaims beneficial ownership of these securities except to the extent of his pecuniary interest therein.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>John J. Koraleski</signatureName>
        <signatureDate>2003-06-09</signatureDate>
    </ownerSignature>

</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----
