UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  SCHEDULE 13G

                    Under the Securities Exchange Act of 1934

                               (Amendment No. 1)*

                              Glacier Bancorp, Inc.
                                (Name of Issuer)

                                   Common Stock
                         (Title of Class of Securities)

                                    37637Q105
                                 (CUSIP Number)

                                December 31, 2003
             (Date of Event Which Requires Filing of this Statement)

            Check the appropriate box to designate the rule pursuant
                        to which this Schedule is filed:

                                [X] Rule 13d-1(b)

                                [ ] Rule 13d-1(c)

                                [ ] Rule 13d-1(d)

*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter the
disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).

                               Page 1 of 10 pages

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CUSIP No. 37637Q105                   13G                     Page 2 of 10 Pages
- --------------------------                                    ------------------

- --------------------------------------------------------------------------------
1    NAME OF REPORTING PERSON
     S.S. or I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

          Columbia Wanger Asset Management, L.P. 36-3820584

- --------------------------------------------------------------------------------
2    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*

          Not Applicable                                                  (a)[ ]
                                                                          (b)[ ]

- --------------------------------------------------------------------------------
3    SEC USE ONLY

- --------------------------------------------------------------------------------
4    CITIZENSHIP OR PLACE OF ORGANIZATION

          Delaware

- --------------------------------------------------------------------------------
                    5    SOLE VOTING POWER

NUMBER OF SHARES            None

                    ------------------------------------------------------------
BENEFICIALLY        6    SHARED VOTING POWER
OWNED BY
                            1,236,379

                    ------------------------------------------------------------
EACH                7    SOLE DISPOSITIVE POWER
REPORTING
                            None

                    ------------------------------------------------------------
                    8    SHARED DISPOSITIVE POWER
PERSON WITH
                            1,236,379

- --------------------------------------------------------------------------------
9    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

          1,236,379

- --------------------------------------------------------------------------------
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*

          Not Applicable                                                     [ ]

- --------------------------------------------------------------------------------
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

          6.4 %

- --------------------------------------------------------------------------------
12   TYPE OF REPORTING PERSON*

          IA

- --------------------------------------------------------------------------------

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CUSIP No. 37637Q105                   13G                     Page 3 of 10 Pages
- --------------------------                                    ------------------

- --------------------------------------------------------------------------------
1    NAME OF REPORTING PERSON
     S.S. or I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

          WAM Acquisition GP, Inc.

- --------------------------------------------------------------------------------
2    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*

          Not Applicable                                                  (a)[ ]
                                                                          (b)[ ]

- --------------------------------------------------------------------------------
3    SEC USE ONLY

- --------------------------------------------------------------------------------
4    CITIZENSHIP OR PLACE OF ORGANIZATION

          Delaware

- --------------------------------------------------------------------------------
                    5    SOLE VOTING POWER

NUMBER OF SHARES            None

                    ------------------------------------------------------------
BENEFICIALLY        6    SHARED VOTING POWER

OWNED BY                    1,236,379

                    ------------------------------------------------------------
EACH                7    SOLE DISPOSITIVE POWER

REPORTING                   None

                    ------------------------------------------------------------
                    8    SHARED DISPOSITIVE POWER
PERSON WITH
                            1,236,379

- --------------------------------------------------------------------------------
9    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

          1,236,379

- --------------------------------------------------------------------------------
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*

          Not Applicable                                                     [ ]

- --------------------------------------------------------------------------------
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

          6.4 %

- --------------------------------------------------------------------------------
12   TYPE OF REPORTING PERSON*

          CO

- --------------------------------------------------------------------------------

- --------------------------                                    -----------------
CUSIP No. 37637Q105                   13G                     Page 4 of 10 Page
- --------------------------                                    -----------------

- --------------------------------------------------------------------------------
1    NAME OF REPORTING PERSON
     S.S. or I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

          Columbia Acorn Trust

- --------------------------------------------------------------------------------
2    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*

          Not Applicable                                                  (a)[ ]
                                                                          (b)[ ]
- --------------------------------------------------------------------------------
3    SEC USE ONLY
- --------------------------------------------------------------------------------
4    CITIZENSHIP OR PLACE OF ORGANIZATION

          Massachusetts

- --------------------------------------------------------------------------------
                    5    SOLE VOTING POWER
NUMBER OF SHARES
                            None

                    ------------------------------------------------------------
BENEFICIALLY        6    SHARED VOTING POWER

OWNED BY                    1,122,000

                    ------------------------------------------------------------
EACH                7    SOLE DISPOSITIVE POWER

REPORTING                   None

                    ------------------------------------------------------------
                    8    SHARED DISPOSITIVE POWER

PERSON WITH                 1,122,000

- --------------------------------------------------------------------------------
9    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

          1,122,000

- --------------------------------------------------------------------------------
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*

          Not Applicable                                                     [ ]

- --------------------------------------------------------------------------------
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

          5.8 %

- --------------------------------------------------------------------------------
12   TYPE OF REPORTING PERSON*

          IV

- --------------------------------------------------------------------------------

Item 1(a)  Name of Issuer:

              Glacier Bancorp, Inc.

Item 1(b)  Address of Issuer's Principal Executive Offices:

              49 Commons Loop
              Kalispell, Montana 59901

Item 2(a)  Name of Person Filing:

              Columbia Wanger Asset Management, L.P. ("WAM")
              WAM Acquisition GP, Inc., the general partner of WAM
              ("WAM GP")
              Columbia Acorn Trust ("Acorn")

Item 2(b)  Address of Principal Business Office:

              WAM, WAM GP, and Acorn are all located at:

              227 West Monroe Street, Suite 3000
              Chicago, Illinois  60606

Item 2(c)  Citizenship:

              WAM is a Delaware limited partnership; WAM GP is a Delaware
              corporation; and Acorn is a Massachusetts business trust.

Item 2(d)  Title of Class of Securities:

              Common Stock

Item 2(e)  CUSIP Number:

              37637Q105

Item 3     Type of Person:

              (d)  Acorn is an Investment Company under section 8 of the
                   Investment Company Act.

              (e)  WAM is an Investment Adviser registered under section 203 of
                   the Investment Advisers Act of 1940; WAM GP is the General
                   Partner of the Investment Adviser.

                               Page 5 of 10 pages

Item 4     Ownership (at December 31, 2003):

              (a)  Amount owned "beneficially" within the meaning of rule
                   13d-3:

                   1,236,379

              (b)  Percent of class:

                   6.4 % (based on 19,339,470 shares outstanding as of November
                   3, 2003)

              (c)  Number of shares as to which such person has:

                         (i)   sole power to vote or to direct
                               the vote: none

                         (ii)  shared power to vote or to
                               direct the vote: 1,236,379

                         (iii) sole power to dispose or to
                               direct the disposition of: none

                         (iv)  shared power to dispose or to
                               direct disposition of: 1,236,379

Item 5     Ownership of Five Percent or Less of a Class:

              Not Applicable

Item 6     Ownership of More than Five Percent on Behalf of Another Person:

              The shares reported herein have been acquired on behalf of
              discretionary clients of WAM, including Acorn. Persons other than
              WAM and WAM GP are entitled to receive all dividends from, and
              proceeds from the sale of, those shares. Acorn is the only such
              person known to be entitled to all dividends from, and all
              proceeds from the sale of, shares reported herein to the extent
              of more than 5% of the class.

Item 7     Identification and Classification of the Subsidiary Which Acquired
           the Security Being Reported on by the Parent Holding Company:

              Not Applicable

Item 8     Identification and Classification of Members of the Group:

              Not Applicable

Item 9     Notice of Dissolution of Group:

              Not Applicable

                                  Page 6 of 10 pages

Item 10    Certification:

               By signing below I certify that, to the best of my knowledge
           and belief, the securities referred to above were acquired and
           are held in the ordinary course of business and were not acquired
           and are not held for the purpose of or with the effect of
           changing or influencing the control of the issuer of the
           securities and were not acquired and are not held in connection
           with or as a participant in any transaction having that purpose
           or effect.

                               Page 7 of 10 pages

                                    Signature

     After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.

Date: February 13, 2004

                    The undersigned corporation, on the date above written,
                    agrees and consents to the joint filing on its behalf of
                    this Schedule 13G in connection with its beneficial
                    ownership of the security reported herein.

                                        WAM Acquisition GP, Inc.
                                           for itself and as general partner of
                                           COLUMBIA WANGER ASSET
                                           MANAGEMENT, L.P.

                                        By: /s/ Bruce H. Lauer
                                            ------------------------------------
                                                Bruce H. Lauer
                                                Senior Vice President and
                                                Secretary

                    The undersigned trust, on the date above written, agrees and
                    consents to the joint filing on its behalf of this Schedule
                    13G in connection with its beneficial ownership of the
                    security reported herein.

                                        COLUMBIA ACORN TRUST

                                        By: /s/ Bruce H. Lauer
                                            ------------------------------------
                                                Bruce H. Lauer
                                                Vice President, Treasurer and
                                                Secretary

                              Pages 8 of 10 pages

                                  Exhibit Index

Exhibit 1     Joint Filing Agreement dated as of February 13, 2004 by and
              among Columbia Wanger Asset Management, L.P., WAM Acquisition GP,
              Inc., and Columbia Acorn Trust.

                               Page 9 of 10 pages

                                                                       EXHIBIT 1

                             JOINT FILING AGREEMENT

     The undersigned hereby agree to the joint filing of the Schedule 13G to
which this Agreement is attached.

              Dated: February 13, 2004

                                        WAM Acquisition GP, Inc.
                                            for itself and as general partner of
                                            COLUMBIA WANGER ASSET
                                            MANAGEMENT, L.P.

                                        By: /s/ Bruce H. Lauer
                                            ------------------------------------
                                                Bruce H. Lauer
                                                Senior Vice President and
                                                Secretary

                                        COLUMBIA ACORN TRUST

                                        By: /s/ Bruce H. Lauer
                                            ------------------------------------
                                                Bruce H. Lauer
                                                Vice President, Treasurer and
                                                Secretary

                              Page 10 of 10 pages