<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-06-07</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001227314</rptOwnerCik>
            <rptOwnerName>HOPE RICHARDS JUDITH</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>PAUL HASTINGS JANOFSKY &amp; WALKER</rptOwnerStreet1>
            <rptOwnerStreet2>875 15TH STREET NW</rptOwnerStreet2>
            <rptOwnerCity>WASHINGTON</rptOwnerCity>
            <rptOwnerState>DC</rptOwnerState>
            <rptOwnerZipCode>20005</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>2005-06-07</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>900</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>66.76</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4485</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2005-06-07</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>600</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>66.73</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>by Trust</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The reporting person originally purchased the securities in June 2002, under authority granted to her in a power of attorney and as co-trustee of a revocable trust for the account and benefit of Joseph C. Richards, the father of the reporting person. The revocable trust converted to an irrevocable trust for the account and benefit of the children of the reporting person.  The reporting person currently is the trustee of this irrevocable trust.  The reporting person disclaims beneficial ownership of such securities, and the filing of this report does not constitute and should not be deemed an admission that the reporting person is the beneficial owner of such securities.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>By: Laura A. Heisterkamp  For: Judith R. Hope</signatureName>
        <signatureDate>2005-06-09</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0202
4
2005-06-07
0
0000100885
UNION PACIFIC CORP
UNP
0001227314
HOPE RICHARDS JUDITH
PAUL HASTINGS JANOFSKY & WALKER
875 15TH STREET NW
WASHINGTON
DC
20005
1
0
0
0
Common Stock
2005-06-07
4
S
0
900
66.76
D
4485
D
Common Stock
2005-06-07
4
S
0
600
66.73
D
0
I
by Trust
The reporting person originally purchased the securities in June 2002, under authority granted to her in a power of attorney and as co-trustee of a revocable trust for the account and benefit of Joseph C. Richards, the father of the reporting person. The revocable trust converted to an irrevocable trust for the account and benefit of the children of the reporting person.  The reporting person currently is the trustee of this irrevocable trust.  The reporting person disclaims beneficial ownership of such securities, and the filing of this report does not constitute and should not be deemed an admission that the reporting person is the beneficial owner of such securities.
By: Laura A. Heisterkamp  For: Judith R. Hope
2005-06-09