0001193125-07-075650 DFAN14A 2 20070405 20070405 20070405 COLUMBIA BANKING SYSTEM INC 0000887343 6022 911422237 WA 1231 DFAN14A 34 000-20288 07752847 1102 BROADWAY PLAZA TACOMA WA 98402 2533051900 1102 BROADWAY PLAZA TACOMA WA 98402 MOUNTAIN BANK HOLDING CO 0000898018 6021 911602736 WA 1231 DFAN14A 501 ROOSEVELT AVE EAST PO BOX 98 ENUMCLAW WA 98022 2068250100 501 ROOSEVELE AVENUE ENUMCLAW WA 98022 DFAN14A 1 d8k.htm FORM 8-K EX-2.1 2 dex21.htm PLAN AND AGREEMENT OF MERGER