<SUBMISSION>
<ACCESSION-NUMBER>0001193125-07-160564
<TYPE>8-K
<PUBLIC-DOCUMENT-COUNT>2
<PERIOD>20070723
<ITEMS>2.01
<ITEMS>9.01
<FILING-DATE>20070724
<DATE-OF-FILING-DATE-CHANGE>20070724
<FILER>
<COMPANY-DATA>
<CONFORMED-NAME>COLUMBIA BANKING SYSTEM INC
<CIK>0000887343
<ASSIGNED-SIC>6022
<IRS-NUMBER>911422237
<STATE-OF-INCORPORATION>WA
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<FILING-VALUES>
<FORM-TYPE>8-K
<ACT>34
<FILE-NUMBER>000-20288
<FILM-NUMBER>07995694
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>1102 BROADWAY PLAZA
<CITY>TACOMA
<STATE>WA
<ZIP>98402
<PHONE>2533051900
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>1102 BROADWAY PLAZA
<CITY>TACOMA
<STATE>WA
<ZIP>98402
</MAIL-ADDRESS>
</FILER>
<DOCUMENT>
<TYPE>8-K
<SEQUENCE>1
<FILENAME>d8k.htm
<DESCRIPTION>FORM 8-K
<TEXT>
<HTML><HEAD>
<TITLE>Form 8-K</TITLE>
</HEAD>
 <BODY BGCOLOR="WHITE">

<HR SIZE="3" NOSHADE COLOR="#000000" ALIGN="left"> <P STYLE="margin-top:3px;margin-bottom:0px" ALIGN="center"><FONT FACE="Times New Roman" SIZE="5"><B>SECURITIES AND EXCHANGE COMMISSION </B></FONT></P> <P
STYLE="margin-top:0px;margin-bottom:0px" ALIGN="center"><FONT FACE="Times New Roman" SIZE="3"><B>Washington, D.C. 20549 </B></FONT></P> <P STYLE="font-size:12px;margin-top:0px;margin-bottom:0px">&nbsp;</P><HR WIDTH="17%" SIZE="1" NOSHADE
COLOR="#000000"> <P STYLE="margin-top:12px;margin-bottom:0px" ALIGN="center"><FONT FACE="Times New Roman" SIZE="5"><B>FORM 8-K </B></FONT></P> <P STYLE="font-size:12px;margin-top:0px;margin-bottom:0px">&nbsp;</P><HR WIDTH="17%" SIZE="1" NOSHADE
COLOR="#000000"> <P STYLE="margin-top:12px;margin-bottom:0px" ALIGN="center"><FONT FACE="Times New Roman" SIZE="3"><B>CURRENT REPORT </B></FONT></P> <P STYLE="margin-top:12px;margin-bottom:0px" ALIGN="center"><FONT FACE="Times New Roman"
SIZE="3"><B>Pursuant to Section&nbsp;13 or 15(d) of </B></FONT></P> <P STYLE="margin-top:0px;margin-bottom:0px" ALIGN="center"><FONT FACE="Times New Roman" SIZE="3"><B>the Securities Exchange Act of 1934 </B></FONT></P> <P
STYLE="margin-top:12px;margin-bottom:0px" ALIGN="center"><FONT FACE="Times New Roman" SIZE="2"><B>Date of Report (Date of earliest event reported): </B></FONT></P> <P STYLE="margin-top:12px;margin-bottom:0px" ALIGN="center"><FONT
FACE="Times New Roman" SIZE="2"><B>July&nbsp;23, 2007 </B></FONT></P> <P STYLE="font-size:12px;margin-top:0px;margin-bottom:0px">&nbsp;</P><HR WIDTH="17%" SIZE="1" NOSHADE COLOR="#000000"> <P STYLE="margin-top:12px;margin-bottom:0px"
ALIGN="center"><FONT FACE="Times New Roman" SIZE="6"><B>COLUMBIA BANKING SYSTEM, INC. </B></FONT></P> <P STYLE="margin-top:0px;margin-bottom:0px" ALIGN="center"><FONT FACE="Times New Roman" SIZE="1"><B>(Exact name of registrant as specified in its
charter) </B></FONT></P> <P STYLE="font-size:12px;margin-top:0px;margin-bottom:0px">&nbsp;</P><HR WIDTH="17%" SIZE="1" NOSHADE COLOR="#000000"> <P STYLE="margin-top:12px;margin-bottom:0px" ALIGN="center"><FONT FACE="Times New Roman"
SIZE="2"><B>Washington </B></FONT></P> <P STYLE="margin-top:0px;margin-bottom:0px" ALIGN="center"><FONT FACE="Times New Roman" SIZE="1"><B>(State or other jurisdiction of incorporation) </B></FONT></P> <P
STYLE="font-size:12px;margin-top:0px;margin-bottom:0px">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" ALIGN="center">

<TR>
<TD WIDTH="50%"></TD>
<TD VALIGN="bottom" WIDTH="2%"></TD>
<TD WIDTH="48%"></TD></TR>
<TR>
<TD VALIGN="top" ALIGN="center"><FONT FACE="Times New Roman" SIZE="2"><B>0-20288</B></FONT></TD>
<TD VALIGN="bottom"><FONT SIZE="1">&nbsp;</FONT></TD>
<TD VALIGN="top" ALIGN="center"><FONT FACE="Times New Roman" SIZE="2"><B>91-1422237</B></FONT></TD></TR>
<TR>
<TD VALIGN="top" ALIGN="center"><FONT FACE="Times New Roman" SIZE="1"><B>(Commission File Number)</B></FONT></TD>
<TD VALIGN="bottom"><FONT SIZE="1">&nbsp;</FONT></TD>
<TD VALIGN="top" ALIGN="center"><FONT FACE="Times New Roman" SIZE="1"><B>IRS Employer Identification No.</B></FONT></TD></TR>
</TABLE> <P STYLE="margin-top:12px;margin-bottom:0px" ALIGN="center"><FONT FACE="Times New Roman" SIZE="2"><B>1301 A Street </B></FONT></P> <P STYLE="margin-top:0px;margin-bottom:0px" ALIGN="center"><FONT
FACE="Times New Roman" SIZE="2"><B>Tacoma, WA 98402 </B></FONT></P> <P STYLE="margin-top:0px;margin-bottom:0px" ALIGN="center"><FONT FACE="Times New Roman" SIZE="1"><B>(Address of principal executive offices) (zip code) </B></FONT></P> <P
STYLE="margin-top:12px;margin-bottom:0px" ALIGN="center"><FONT FACE="Times New Roman" SIZE="2"><B>Registrant&#146;s telephone number, including area code: (253)&nbsp;305-1900 </B></FONT></P> <P
STYLE="font-size:12px;margin-top:0px;margin-bottom:0px">&nbsp;</P> <P STYLE="margin-top:12px;margin-bottom:0px" ALIGN="center"><FONT FACE="Times New Roman" SIZE="1"><B>(Former Name or former address, if changed since last report.) </B></FONT></P> <P
STYLE="font-size:12px;margin-top:0px;margin-bottom:0px">&nbsp;</P><HR WIDTH="17%" SIZE="1" NOSHADE COLOR="#000000"> <P STYLE="margin-top:12px;margin-bottom:0px"><FONT FACE="Times New Roman" SIZE="2">Check the appropriate box below if the Form 8-K
filing is intended to simultaneously satisfy the filing obligations of the registrant under any of the following provisions: </FONT></P> <P STYLE="font-size:12px;margin-top:0px;margin-bottom:0px">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><FONT FACE="Times New Roman" SIZE="2"></FONT><FONT FACE="WINGDINGS" SIZE="2" COLOR="#000000">&#168;</FONT><FONT FACE="Times New Roman" SIZE="2"></FONT></TD>
<TD ALIGN="left" VALIGN="top"><FONT FACE="Times New Roman" SIZE="2">Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) </FONT></TD></TR></TABLE> <P STYLE="font-size:12px;margin-top:0px;margin-bottom:0px">&nbsp;</P>

<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><FONT FACE="Times New Roman" SIZE="2"></FONT><FONT FACE="WINGDINGS" SIZE="2" COLOR="#000000">&#168;</FONT><FONT FACE="Times New Roman" SIZE="2"></FONT></TD>
<TD ALIGN="left" VALIGN="top"><FONT FACE="Times New Roman" SIZE="2">Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) </FONT></TD></TR></TABLE> <P
STYLE="font-size:12px;margin-top:0px;margin-bottom:0px">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><FONT FACE="Times New Roman" SIZE="2"></FONT><FONT FACE="WINGDINGS" SIZE="2" COLOR="#000000">&#168;</FONT><FONT FACE="Times New Roman" SIZE="2"></FONT></TD>
<TD ALIGN="left" VALIGN="top"><FONT FACE="Times New Roman" SIZE="2">Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act of (17 CFR 240.14d-2(b)) </FONT></TD></TR></TABLE> <P
STYLE="font-size:12px;margin-top:0px;margin-bottom:0px">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="4%" VALIGN="top" ALIGN="left"><FONT FACE="Times New Roman" SIZE="2"></FONT><FONT FACE="WINGDINGS" SIZE="2" COLOR="#000000">&#168;</FONT><FONT FACE="Times New Roman" SIZE="2"></FONT></TD>
<TD ALIGN="left" VALIGN="top"><FONT FACE="Times New Roman" SIZE="2">Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act of (17 CFR 240.13e-4(c)) </FONT></TD></TR></TABLE> <P
STYLE="font-size:6px;margin-top:0px;margin-bottom:0px">&nbsp;</P><HR SIZE="3" NOSHADE COLOR="#000000" ALIGN="left">

<p Style='page-break-before:always'>
<HR  SIZE="3" COLOR="#999999" WIDTH="100%" ALIGN="CENTER">


<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="9%" VALIGN="top" ALIGN="left"><FONT FACE="Times New Roman" SIZE="2"><B>Item&nbsp;2.01.</B></FONT></TD>
<TD ALIGN="left" VALIGN="top"><FONT FACE="Times New Roman" SIZE="2"><B>Completion of Acquisition or Disposition of Assets </B></FONT></TD></TR></TABLE> <P STYLE="margin-top:6px;margin-bottom:0px"><FONT FACE="Times New Roman" SIZE="2">On
July&nbsp;23, 2007, Columbia Banking System, Inc. (&#147;Columbia&#148;) completed its two pending acquisitions. Columbia acquired Mountain Bank Holding Company (&#147;MBHC&#148;), a Washington corporation, and its subsidiary bank, Mt. Rainier
National Bank, a national banking association headquartered in Enumclaw, Washington. Columbia also acquired Town Center Bancorp (&#147;TWBC&#148;), an Oregon corporation, and its subsidiary bank, Town Center Bank, a commercial bank headquartered in
Portland, Oregon. </FONT></P> <P STYLE="margin-top:12px;margin-bottom:0px"><FONT FACE="Times New Roman" SIZE="2">Under the terms of the merger agreement between Columbia and Mountain Bank Holding Company, MBHC merged with and into Columbia, and Mt.
Rainier National Bank merged with and into Columbia State Bank. The acquisition was accomplished pursuant to a Plan and Agreement of Merger whereby shareholder of MBHC will receive a &#147;unit&#148; consisting of .4231 shares of Columbia common
stock and cash in an amount of $11.25. Columbia will issue an aggregate of 993,932 shares of its common stock and pay a total of $26,428,106 to MBHC shareholders. </FONT></P> <P STYLE="margin-top:12px;margin-bottom:0px"><FONT FACE="Times New Roman"
SIZE="2">Under the terms of the merger agreement between Columbia and Town Center, TWBC merged with and into Columbia, and Town Center Bank merged with and into Columbia&#146;s subsidiary, Columbia State Bank. The acquisition was accomplished
pursuant to a Plan and Agreement of Merger pursuant to which shareholders of TWBC elected to receive a &#147;unit&#148; comprised of .3391 shares of Columbia common stock and cash in an amount of $9.382. Columbia will issue an aggregate of 704,839
shares of its common stock and pay a total of $19,501,021 to TWBC shareholders. </FONT></P> <P STYLE="margin-top:12px;margin-bottom:0px"><FONT FACE="Times New Roman" SIZE="2">The Agreement between Columbia and MBHC was included as Appendix A to the
Proxy Statement/Prospectus dated May&nbsp;17, 2007, and the Agreement between Columbia and Town Center was included as Appendix A to the Proxy Statement/Prospectus dated June&nbsp;13, 2007, previously filed by Columbia as part of its Registration
Statement on Form S-4 with the Securities and Exchange Commission. A copy of the press release dated July&nbsp;23, 2007, which is attached as Exhibit 99.1 is incorporated herein by reference. </FONT></P> <P
STYLE="font-size:18px;margin-top:0px;margin-bottom:0px">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="9%" VALIGN="top" ALIGN="left"><FONT FACE="Times New Roman" SIZE="2"><B>Item&nbsp;9.01.</B></FONT></TD>
<TD ALIGN="left" VALIGN="top"><FONT FACE="Times New Roman" SIZE="2"><B>Financial Statements and Exhibits </B></FONT></TD></TR></TABLE> <P STYLE="font-size:6px;margin-top:0px;margin-bottom:0px">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="8%"><FONT SIZE="1">&nbsp;</FONT></TD>
<TD WIDTH="5%" VALIGN="top" ALIGN="left"><FONT FACE="Times New Roman" SIZE="2">(a)</FONT></TD>
<TD ALIGN="left" VALIGN="top"><FONT FACE="Times New Roman" SIZE="2">Financial statements &#150; not applicable </FONT></TD></TR></TABLE> <P STYLE="font-size:6px;margin-top:0px;margin-bottom:0px">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="8%"><FONT SIZE="1">&nbsp;</FONT></TD>
<TD WIDTH="5%" VALIGN="top" ALIGN="left"><FONT FACE="Times New Roman" SIZE="2">(b)</FONT></TD>
<TD ALIGN="left" VALIGN="top"><FONT FACE="Times New Roman" SIZE="2">Pro forma financial information &#150; not applicable </FONT></TD></TR></TABLE> <P STYLE="font-size:6px;margin-top:0px;margin-bottom:0px">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="8%"><FONT SIZE="1">&nbsp;</FONT></TD>
<TD WIDTH="5%" VALIGN="top" ALIGN="left"><FONT FACE="Times New Roman" SIZE="2">(c)</FONT></TD>
<TD ALIGN="left" VALIGN="top"><FONT FACE="Times New Roman" SIZE="2">Shell company transactions&#151;not applicable </FONT></TD></TR></TABLE> <P STYLE="font-size:6px;margin-top:0px;margin-bottom:0px">&nbsp;</P>
<TABLE STYLE="BORDER-COLLAPSE:COLLAPSE" BORDER="0" CELLPADDING="0" CELLSPACING="0" WIDTH="100%">
<TR>
<TD WIDTH="8%"><FONT SIZE="1">&nbsp;</FONT></TD>
<TD WIDTH="5%" VALIGN="top" ALIGN="left"><FONT FACE="Times New Roman" SIZE="2">(d)</FONT></TD>
<TD ALIGN="left" VALIGN="top"><FONT FACE="Times New Roman" SIZE="2">Exhibits </FONT></TD></TR></TABLE> <P STYLE="font-size:12px;margin-top:0px;margin-bottom:0px">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="80%" BORDER="0" ALIGN="center">

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<TD></TD>
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<TD WIDTH="94%"></TD></TR>
<TR>
<TD VALIGN="top"><FONT FACE="Times New Roman" SIZE="2">99.1</FONT></TD>
<TD VALIGN="bottom"><FONT SIZE="1">&nbsp;&nbsp;</FONT></TD>
<TD VALIGN="bottom"><FONT FACE="Times New Roman" SIZE="2">Press Release dated July&nbsp;23, 2007 announcing the closing of the transactions.</FONT></TD></TR>
</TABLE> <P STYLE="margin-top:0px;margin-bottom:0px"><FONT SIZE="1">&nbsp;</FONT></P>
 <P STYLE="margin-top:0px;margin-bottom:0px" ALIGN="center"><FONT FACE="Times New Roman" SIZE="2">1 </FONT></P>


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 <P STYLE="margin-top:0px;margin-bottom:0px" ALIGN="center"><FONT FACE="Times New Roman" SIZE="2"><B>SIGNATURES </B></FONT></P> <P STYLE="margin-top:12px;margin-bottom:0px; text-indent:4%"><FONT
FACE="Times New Roman" SIZE="2">Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. </FONT></P> <P
STYLE="font-size:12px;margin-top:0px;margin-bottom:0px">&nbsp;</P>
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<TD WIDTH="48%"></TD>
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<TD WIDTH="2%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="48%"></TD></TR>
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<TD VALIGN="top"> <P STYLE="text-indent:2.00em"><FONT FACE="Times New Roman" SIZE="2">Dated: July&nbsp;23, 2007</FONT></P></TD>
<TD VALIGN="bottom"><FONT SIZE="1">&nbsp;</FONT></TD>
<TD VALIGN="bottom" COLSPAN="3"><FONT FACE="Times New Roman" SIZE="2">COLUMBIA BANKING SYSTEM, INC.</FONT></TD></TR>
<TR>
<TD HEIGHT="16"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD>
<TD HEIGHT="16" COLSPAN="2"></TD></TR>
<TR>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom"><FONT SIZE="1">&nbsp;</FONT></TD>
<TD VALIGN="bottom"><FONT FACE="Times New Roman" SIZE="2">By:</FONT></TD>
<TD VALIGN="bottom"><FONT SIZE="1">&nbsp;</FONT></TD>
<TD VALIGN="bottom"> <P STYLE="margin-bottom:1px;border-bottom:1px solid #000000"><FONT FACE="Times New Roman" SIZE="2">/s/ Melanie J. Dressel</FONT></P></TD></TR>
<TR>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom"><FONT SIZE="1">&nbsp;</FONT></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"><FONT SIZE="1">&nbsp;</FONT></TD>
<TD VALIGN="bottom"><FONT FACE="Times New Roman" SIZE="2">Melanie J. Dressel</FONT></TD></TR>
<TR>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom"><FONT SIZE="1">&nbsp;</FONT></TD>
<TD VALIGN="bottom"></TD>
<TD VALIGN="bottom"><FONT SIZE="1">&nbsp;</FONT></TD>
<TD VALIGN="bottom"><FONT FACE="Times New Roman" SIZE="2">President and Chief Executive Officer</FONT></TD></TR>
</TABLE> <P STYLE="margin-top:0px;margin-bottom:0px"><FONT SIZE="1">&nbsp;</FONT></P>
 <P STYLE="margin-top:0px;margin-bottom:0px" ALIGN="center"><FONT FACE="Times New Roman" SIZE="2">2 </FONT></P>

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</DOCUMENT>
<DOCUMENT>
<TYPE>EX-99.1
<SEQUENCE>2
<FILENAME>dex991.htm
<DESCRIPTION>PRESS RELEASE
<TEXT>
<HTML><HEAD>
<TITLE>Press Release</TITLE>
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 <P STYLE="margin-top:0px;margin-bottom:0px" ALIGN="right"><FONT FACE="Times New Roman" SIZE="2"><B>Exhibit 99.1 </B></FONT></P> <P STYLE="margin-top:12px;margin-bottom:0px" ALIGN="right"><FONT
FACE="Times New Roman" SIZE="2"><B><U>FOR IMMEDIATE RELEASE</U> </B></FONT></P> <P STYLE="margin-top:0px;margin-bottom:0px" ALIGN="right"><FONT FACE="Times New Roman" SIZE="2"><B>July&nbsp;23, 2007 </B></FONT></P> <P
STYLE="font-size:12px;margin-top:0px;margin-bottom:0px">&nbsp;</P>
<TABLE CELLSPACING="0" CELLPADDING="0" WIDTH="100%" BORDER="0" ALIGN="center">

<TR>
<TD WIDTH="18%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="21%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="21%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="20%"></TD>
<TD VALIGN="bottom" WIDTH="1%"></TD>
<TD WIDTH="16%"></TD></TR>
<TR>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom"><FONT SIZE="1">&nbsp;</FONT></TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom"><FONT SIZE="1">&nbsp;</FONT></TD>
<TD VALIGN="top"></TD>
<TD VALIGN="bottom"><FONT SIZE="1">&nbsp;</FONT></TD>
<TD VALIGN="top"><FONT FACE="Times New Roman" SIZE="2">Contacts:</FONT></TD>
<TD VALIGN="bottom"><FONT SIZE="1">&nbsp;&nbsp;</FONT></TD>
<TD VALIGN="top" NOWRAP ALIGN="right"><FONT FACE="Times New Roman" SIZE="2"><B>Melanie&nbsp;J.&nbsp;Dressel,</B>&nbsp;President&nbsp;and</FONT></TD></TR>
</TABLE> <P STYLE="margin-top:0px;margin-bottom:0px" ALIGN="right"><FONT FACE="Times New Roman" SIZE="2">Chief Executive Officer </FONT></P> <P STYLE="margin-top:0px;margin-bottom:0px" ALIGN="right"><FONT
FACE="Times New Roman" SIZE="2">(253) 305-1911 </FONT></P> <P STYLE="margin-top:12px;margin-bottom:0px" ALIGN="right"><FONT FACE="Times New Roman" SIZE="2"><B>Gary R. Schminkey</B>, Executive Vice President </FONT></P> <P
STYLE="margin-top:0px;margin-bottom:0px" ALIGN="right"><FONT FACE="Times New Roman" SIZE="2">and Chief Financial Officer </FONT></P> <P STYLE="margin-top:0px;margin-bottom:0px" ALIGN="right"><FONT FACE="Times New Roman" SIZE="2">(253) 305-1966
</FONT></P> <P STYLE="margin-top:12px;margin-bottom:0px" ALIGN="center"><FONT FACE="Times New Roman" SIZE="2"><B>COLUMBIA BANKING SYSTEM COMPLETES ACQUISITIONS OF MOUNTAIN BANK </B></FONT></P> <P STYLE="margin-top:0px;margin-bottom:0px"
ALIGN="center"><FONT FACE="Times New Roman" SIZE="2"><B>HOLDING COMPANY AND TOWN CENTER BANCORP </B></FONT></P> <P STYLE="margin-top:12px;margin-bottom:0px"><FONT FACE="Times New Roman" SIZE="2"><B><I>TACOMA,
Washington</I></B><I></I><B><I></I></B>&#151;Columbia Banking System, Inc. (NASDAQ: COLB) (&#147;Columbia&#148;) today announced the completion of its acquisitions of Mountain Bank Holding Company, the parent company of Mt. Rainier National Bank,
and Town Center Bancorp, the parent company of Town Center Bank. Shareholders of both organizations overwhelmingly approved the transactions, and all regulatory approvals have been received. With the completion of the mergers, Columbia&#146;s total
assets approach $3 billion, with 53 branches in nine counties in Washington and Oregon. </FONT></P> <P STYLE="margin-top:12px;margin-bottom:0px; text-indent:4%"><FONT FACE="Times New Roman" SIZE="2">Melanie J. Dressel, President and Chief Executive
Officer of Columbia said, &#147;We are delighted to welcome Mt. Rainier and Town Center customers, employees and shareholders to the Columbia family. We are joining forces with two well-run, profitable organizations that have strong cultural
similarities, talented management and employees, and the same dedication to the best possible customer service. As we expand our geographic footprint into adjacent markets, we are moving significantly closer to our goal of becoming a Pacific
Northwest regional community bank.&#148; </FONT></P> <P STYLE="margin-top:12px;margin-bottom:0px; text-indent:4%"><FONT FACE="Times New Roman" SIZE="2">Effective today, Mt. Rainier National Bank has been merged into Columbia State Bank, a subsidiary
of Columbia Banking System, and will do business as Mt. Rainier Bank. Mt. Rainier Bank has seven locations in Washington, including Enumclaw, Buckley, Black Diamond, Auburn, Maple Valley, Sumner, and Federal Way. Town Center Bank has been merged
into Columbia State Bank, adding five Oregon locations in the North Clackamas and Northeast Portland area. </FONT></P> <P STYLE="margin-top:0px;margin-bottom:0px"><FONT SIZE="1">&nbsp;</FONT></P>
 <P STYLE="margin-top:0px;margin-bottom:0px" ALIGN="center"><FONT FACE="Times New Roman" SIZE="2">1 </FONT></P>


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 <P STYLE="margin-top:0px;margin-bottom:0px"><FONT FACE="Times New Roman" SIZE="2"><B>About Columbia </B></FONT></P> <P STYLE="margin-top:6px;margin-bottom:0px; text-indent:8%"><FONT
FACE="Times New Roman" SIZE="2">Columbia Banking System, Inc. is a 53-branch Tacoma-based bank holding company whose wholly owned banking subsidiaries are Columbia Bank and Bank of Astoria. Columbia Bank is a Washington state-chartered full-service
commercial bank; with completion of the mergers, Columbia Bank has 48 banking offices in Pierce, King, Cowlitz, Kitsap and Thurston counties in Washington State, and Clackamas and Multnomah counties in Oregon. Included in Columbia Bank are former
branches of Mt. Rainier National Bank, doing business as Mt. Rainier Bank, with 7 branches in King and Pierce counties. Bank of Astoria, a federally insured commercial bank headquartered in Astoria, Oregon, operates four branches in Clatsop County:
Astoria, Warrenton, Seaside and Cannon Beach; and one branch in Manzanita in Tillamook County. More information about Columbia can be found on its website at <U>www.columbiabank.com</U>. </FONT></P> <P STYLE="margin-top:12px;margin-bottom:0px"
ALIGN="center"><FONT FACE="Times New Roman" SIZE="2">### </FONT></P> <P STYLE="margin-top:24px;margin-bottom:0px" ALIGN="center"><FONT FACE="Times New Roman" SIZE="2">Note Regarding Forward Looking Statements </FONT></P> <P
STYLE="margin-top:12px;margin-bottom:0px"><FONT FACE="Times New Roman" SIZE="2">This news release includes forward looking statements, which management believes are a benefit to shareholders. These forward looking statements describe Columbia&#146;s
management&#146;s expectations regarding future events and developments such as Columbia&#146;s continued growth. The words &#147;goal,&#148; &#147;will,&#148; &#147;believe,&#148; &#147;expect,&#148; &#147;should,&#148; and &#147;anticipate&#148;
and words of similar construction are intended in part to help identify forward looking statements. Future events are difficult to predict, and the expectations described above are necessarily subject to risk and uncertainty that may cause actual
results to differ materially and adversely. In addition to discussions about risks and uncertainties set forth from time to time in Columbia&#146;s filings with the SEC, factors that may cause actual results to differ materially from those
contemplated by such forward looking statements include, among others, the following possibilities: (1)&nbsp;local, national and international economic conditions are less favorable than expected or have a more direct and pronounced effect on
Columbia than expected and adversely affect Columbia&#146;s ability to continue its internal growth at historical rates and maintain the quality of its earning assets; (2)&nbsp;changes in interest rates reduce interest margins more than expected and
negatively affect funding sources; (3)&nbsp;projected business increases following strategic expansion or opening or acquiring new branches are lower than expected; (4)&nbsp;costs or difficulties related to the integration of acquisitions are
greater than expected; (5)&nbsp;competitive pressure among financial institutions increases significantly; (6)&nbsp;legislation or regulatory requirements or changes adversely affect the businesses in which Columbia is engaged. </FONT></P> <P
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