<SUBMISSION>
<ACCESSION-NUMBER>0000715579-09-000014
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20090507
<FILING-DATE>20090507
<DATE-OF-FILING-DATE-CHANGE>20090507
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>LAU WAYNE E
<CIK>0001271299
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>000-11783
<FILM-NUMBER>09803890
</FILING-VALUES>
<MAIL-ADDRESS>
<STREET1>P.O. BOX 493
<CITY>EAST BERLIN
<STATE>PA
<ZIP>17316
</MAIL-ADDRESS>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>ACNB CORP
<CIK>0000715579
<ASSIGNED-SIC>6022
<IRS-NUMBER>232233457
<STATE-OF-INCORPORATION>PA
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>675 OLD HARRISBURG RD
<STREET2>P O BOX 3129
<CITY>GETTYSBURG
<STATE>PA
<ZIP>17325
<PHONE>7173343161
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>P O BOX 3129
<STREET2>675 OLD HARRISBURG RD
<CITY>GETTYSBURG
<STATE>PA
<ZIP>17325
</MAIL-ADDRESS>
</ISSUER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-05-07</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0000715579</issuerCik>
        <issuerName>ACNB CORP</issuerName>
        <issuerTradingSymbol>ACNB</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001271299</rptOwnerCik>
            <rptOwnerName>LAU WAYNE E</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>P.O. BOX 705</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>EAST BERLIN</rptOwnerCity>
            <rptOwnerState>PA</rptOwnerState>
            <rptOwnerZipCode>17316</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Director Emeritus</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <ownerSignature>
        <signatureName>/s/Lynda L. Glass as POA for Wayne E. Lau</signatureName>
        <signatureDate>2009-05-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
