<TABLE> <S> <C>

<PAGE>
 
<ARTICLE> 9
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
FINANCIAL STATEMENTS OF INLAND NORTHWEST BANCORPORATION, INC. AS OF AND FOR THE
SIX MONTHS ENDED JUNE 30, 1998 AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO
SUCH FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000
       
<S>                             <C>
<PERIOD-TYPE>                   6-MOS
<FISCAL-YEAR-END>                          DEC-31-1998
<PERIOD-START>                             JAN-01-1998
<PERIOD-END>                               JUN-30-1998
<CASH>                                           7,289
<INT-BEARING-DEPOSITS>                             120
<FED-FUNDS-SOLD>                                20,375
<TRADING-ASSETS>                                     0
<INVESTMENTS-HELD-FOR-SALE>                     24,435
<INVESTMENTS-CARRYING>                             819
<INVESTMENTS-MARKET>                               828
<LOANS>                                         89,348
<ALLOWANCE>                                      1,284
<TOTAL-ASSETS>                                 146,632
<DEPOSITS>                                     124,763
<SHORT-TERM>                                     8,520
<LIABILITIES-OTHER>                              1,031
<LONG-TERM>                                      2,450
<PREFERRED-MANDATORY>                                0
<PREFERRED>                                          0
<COMMON>                                         9,721
<OTHER-SE>                                         147
<TOTAL-LIABILITIES-AND-EQUITY>                   9,868
<INTEREST-LOAN>                                  4,282
<INTEREST-INVEST>                                  898
<INTEREST-OTHER>                                   353
<INTEREST-TOTAL>                                 5,532
<INTEREST-DEPOSIT>                               2,219
<INTEREST-EXPENSE>                               2,431
<INTEREST-INCOME-NET>                            3,102
<LOAN-LOSSES>                                      220
<SECURITIES-GAINS>                                   0
<EXPENSE-OTHER>                                  2,914
<INCOME-PRETAX>                                    511
<INCOME-PRE-EXTRAORDINARY>                         511
<EXTRAORDINARY>                                      0
<CHANGES>                                            0
<NET-INCOME>                                       278
<EPS-PRIMARY>                                     0.51
<EPS-DILUTED>                                     0.44
<YIELD-ACTUAL>                                    4.43
<LOANS-NON>                                        624
<LOANS-PAST>                                       195
<LOANS-TROUBLED>                                    34
<LOANS-PROBLEM>                                  1,796
<ALLOWANCE-OPEN>                                 1,085
<CHARGE-OFFS>                                       21
<RECOVERIES>                                         0
<ALLOWANCE-CLOSE>                                1,284
<ALLOWANCE-DOMESTIC>                             1,284
<ALLOWANCE-FOREIGN>                                  0
<ALLOWANCE-UNALLOCATED>                              0
        

</TABLE>