FORM 11-K

                      SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C.  20549


   (Mark One)

    [X]     ANNUAL REPORT PURSUANT TO SECTION 15 (d) OF THE
                        SECURITIES EXCHANGE ACT OF 1934

                  For the fiscal year ended December 31, 2003

                                      OR

    [   ]   TRANSITION REPORT PURSUANT TO SECTION 15(d) OF THE
                        SECURITIES EXCHANGE ACT OF 1934

            For the transition period from __________ to __________

                       Commission file number:  1-13923



                       WAUSAU-MOSINEE PAPER CORPORATION
                          SAVINGS AND INVESTMENT PLAN
  (Full title of the plan and the address of the plan, if different from the
                              issuer named below)



                       WAUSAU-MOSINEE PAPER CORPORATION
                            1244 KRONENWETTER DRIVE
                            MOSINEE, WI 54455-9099
          (Name of issuer of the securities held pursuant to the plan
              and the address of its principal executive office)

                       WAUSAU-MOSINEE PAPER CORPORATION


                          SAVINGS AND INVESTMENT PLAN


TABLE OF CONTENTS


                                                                          PAGE

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM                     1

FINANCIAL STATEMENTS:

 Statements of Net Assets Available for Benefits for the

     Years Ended December 31, 2003 and 2002                                 2

 Statements of Changes in Net Assets Available for Benefits for the

     Years Ended December 31, 2003 and 2002                                 3

 Notes to Financial Statements                                             4-9

SUPPLEMENTAL SCHEDULE -

 Form 5500, Schedule H, Part IV, Line 4i - Schedule of Assets
     (Held at End of Year)

     December 31, 2003                                                     10


 Schedules not filed herewith are omitted because of the
   absence of conditions under which they are required.
                                       -i-

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM


  To the Wausau-Mosinee Paper Corporation
  Savings and Investment Plan
  Mosinee, Wisconsin:

We have audited the accompanying statements of net assets available for
benefits of Wausau-Mosinee Paper Corporation Savings and Investment Plan (the
"Plan") as of December 31, 2003 and 2002, and the related statements of changes
in net assets available for benefits for the years then ended.  These financial
statements are the responsibility of the Plan's management.  Our responsibility
is to express an opinion on these financial statements based on our audits.

We conducted our audits in accordance with the standards of the Public Company
Accounting Oversight Board (United States).  Those standards require that we
plan and perform the audit to obtain reasonable assurance about whether the
financial statements are free of material misstatement.  An audit includes
examining, on a test basis, evidence supporting the amounts and disclosures
in the financial statements.  An audit also includes assessing the accounting
principles used and significant estimates made by management, as well as
evaluating the overall financial statement presentation.  We believe that
our audits provide a reasonable basis for our opinion.

In our opinion, such financial statements present fairly, in all material
respects, the net assets available for benefits of the Plan as of December 31,
2003 and 2002, and the changes in net assets available for benefits for the
years then ended in conformity with accounting principles generally accepted in
the United States of America.

Our audits were conducted for the purpose of forming an opinion on the basic
financial statements taken as a whole.  The supplemental schedule listed in the
Table of Contents is presented for the purpose of additional analysis and is
not a required part of the basic financial statements, but is supplementary
information required by the Department of Labor's Rules and Regulations for
Reporting and Disclosure under the Employee Retirement Income Security Act of
1974.  This schedule is the responsibility of the Plan's management.  Such
schedule has been subjected to the auditing procedures applied in our audit of
the basic 2003 financial statements and, in our opinion, is fairly stated in
all material respects when considered in relation to the basic financial
statements taken as a whole.

DELOITTE & TOUCHE LLP


June 25, 2004
                                       -1-



WAUSAU-MOSINEE PAPER CORPORATION
SAVINGS AND INVESTMENT PLAN

STATEMENTS OF NET ASSETS AVAILABLE FOR BENEFITS
DECEMBER 31, 2003 AND 2002


                                                         2003           2002
ASSETS:
                                                             
  Cash and cash equivalents                         $    177,634        $70,669
  Investments                                        168,908,662    134,876,939

  Receivables:
    Employer                                              92,899         79,779
    Participants                                         180,512        113,458
    Accrued income                                       137,169        159,963
Other receivables                                         57,908             --

           Total receivables                             468,488        353,200

           Total assets                              169,554,784    135,300,808

LIABILITIES:
  Other liabilities                                           --        145,328

           Total liabilities                                  --        145,328

NET ASSETS AVAILABLE FOR BENEFITS                   $169,554,784   $135,155,480


See notes to financial statements.
                                       -2-



WAUSAU-MOSINEE PAPER CORPORATION
SAVINGS AND INVESTMENT PLAN

STATEMENTS OF CHANGES IN NET ASSETS AVAILABLE FOR BENEFITS
YEARS ENDED DECEMBER 31, 2003 AND 2002


                                                                            2003                 2002
                                                                                     
ADDITIONS:

  Net appreciation (depreciation) in fair value of investments          $25,884,612        $(24,675,452)
  Contributions:
    Employer                                                              2,622,928           2,548,188
    Participants                                                          9,987,650           9,912,228
    Participant rollovers                                                   135,796             299,393

           Total contributions                                           12,746,374          12,759,809

Interest income                                                           1,893,960           1,755,068
Dividend income                                                             363,554             366,843

           Total additions                                               40,888,500          (9,793,732)

DEDUCTIONS:
   Distributions to participants                                          6,394,359           8,269,827
  Administrative expenses                                                    94,837             115,604

           Total deductions                                               6,489,196           8,385,431

NET INCREASE (DECREASE)                                                  34,399,304         (18,179,163)

NET ASSETS AVAILABLE FOR BENEFITS,
  BEGINNING OF YEAR                                                     135,155,480         153,334,643

NET ASSETS AVAILABLE FOR BENEFITS,
  END OF YEAR                                                          $169,554,784        $135,155,480


See notes to financial statements.
                                       -3-

WAUSAU-MOSINEE PAPER CORPORATION
SAVINGS AND INVESTMENT PLAN

NOTES TO FINANCIAL STATEMENTS
YEARS ENDED DECEMBER 31, 2003 AND 2002


1.  PLAN DESCRIPTION

    The following brief description of the Wausau-Mosinee Paper Corporation
    Savings and Investment Plan (the "Plan") is provided for general
    information purposes only.  The Plan is subject to certain provisions of
    the Employee Retirement Income Security Act of 1974 ("ERISA") and Section
    401 of the Internal Revenue Code ("IRC").  Participants should refer to the
    Plan document for more complete information.

    An employee initially becomes eligible to participate at times varying from
    one day of service to 120 days of service, depending upon the employee's
    classification and his or her employment date.

    General - The Plan was established on January 1, 1988.  It is a defined
    contribution plan that covers all full-time salaried, non-union hourly, and
    all collectively bargained common law employees of Wausau-Mosinee Paper
    Corporation and its subsidiaries (the "Company").

    Contributions - Participants are allowed to contribute up to 16% of their
    gross annual compensation, as defined in the Plan document.  Contributions
    are subject to certain limitations.

    The Plan allows participants to rollover distributions from another
    employer's retirement plan or an annuity contract as contributions, subject
    to certain restrictions.  Participants may deposit any portion of a
    distribution that has not been taxed, provided the deposit is eligible for
    rollover under the IRC.  These deposits are not subject to the contribution
    limitations under the IRC.  The Company does not match these contributions.

    Non-Bargained Employees - The Company currently matches non-bargained
    participant contributions at a rate of $0.50 for every $1.00 contributed on
    the first 3% and $.35 for every $1.00 contributed on the second 3%, up to
    6% of a participant's annual compensation as defined in the Plan.

    The Plan allows the Board of Directors to determine a discretionary
    matching contribution to be made for participants employed on the last day
    of the year or who terminated employment during the year due to death,
    retirement on or after attainment of age 55, or disability.  There were no
    discretionary matching contributions for the years ended December 31, 2003
    and 2002.
                                       -4-
    Bargained Employees - The Company matching contribution differs by
    collective bargaining unit.  Bargained employees of certain collective
    bargaining units do not receive a matching contribution while other
    employees receive a matching contribution.  The maximum matching
    contribution of any collective bargaining unit was $2.03 per $1.00
    contributed up to 3% of a participant's annual gross compensation.

    Participant Accounts - Individual accounts are maintained for each of the
    Plan's participants to reflect the participant's contributions and related
    employer contributions, as well as the participant's share of the Plan's
    income and any related administrative expenses.  Allocations are based on
    the proportion that each participant's account balance has to the total of
    all participants' account balances.

    Investment Options - The Plan allows participants to direct the investment
    of all contributions and related earnings among various mutual funds,
    various pooled equity and fixed income funds and a Company common stock
    fund consisting of common stock of the Company and short-term, interest
    bearing instruments.

    Allocation of Investment Income (Loss) - Each participant's account is
    allocated investment income (loss) based upon the specific investment
    options chosen and in the proportion that an individual participant's
    account balance bears in relation to total account balances under the Plan.

    Vesting - Participants are fully vested in their salary deferral and
    rollover contributions plus earnings/losses thereon.  Vesting in the
    Company's matching contributions, plus actual earnings/losses thereon is
    based on years of service and the participant's employment status as either
    non-bargained or bargained.

    Non-bargained participants are fully vested in the Company's contributions
    after three years of vesting service, or at the rate of 33 1/3% per year of
    service.  Bargained participants vest in the Company's matching
    contributions according to varying vesting schedules depending on the terms
    of the applicable collective bargaining agreement.  A year of vesting
    service consists of a calendar year in which an employee works a minimum of
    1,000 hours for the Company.

    Participant contributions and earnings thereon, rollover contributions, and
    vested Company contributions and earnings thereon may be withdrawn for any
    reason after a participant reaches age 59  1/2 or at any age if a
    participant demonstrates financial hardship.  Financial hardship
    withdrawals are subject to government regulation and may be subject to a
    10% penalty.

    Payment of Benefits - On termination of service due to death, disability,
    or retirement, the vested portion of a participant's account is payable to
    the participant, or a named beneficiary, based on the participant's elected
    payment method.  The payment options available are lump-sum or periodic
    payments.  A nontransferable annuity optional form of benefit was available
    prior to October 1, 2002.
                                       -5-
    Forfeitures - Plan forfeitures arise as a result of participants who
    terminate service with the Company before becoming fully vested in the
    Company's contribution.  These forfeitures are used to reduce future
    Company contributions.  Certain forfeitures relating to the Mosinee Thrift
    Plan prior to January 1, 1999 are allocated to certain participant accounts
    in accordance with the Plan document.  The amount of forfeitures available
    at December 31, 2003 and 2002 was $369,456 and $368,131, respectively.

    Participant Loans - Participants may borrow from their accounts.  Loan
    transactions are treated as a segregated investment of the participant's

    account.  Loan terms range from one to five years or longer if for the
    purchase of a primary residence.  Loans may not exceed the lesser of 50% of
    the participant's account balance or $50,000, and are secured by the
    balance in the participant's account.  The loans bear interest at a rate
    commensurate with local prevailing rates as determined from time to time by
    the Company's employee benefits committee.  Interest rates on existing
    loans range from 4.00% to 10.50%.  Principal and interest are paid ratably
    through payroll deductions.  Upon termination of employment, outstanding
    balances become due and payable to the Plan, unless the borrower elects to
    continue making repayments in accordance with the promissory note
    evidencing the loan.

    Plan Expenses - Recordkeeping and account access fees are charged to
    participants at a cost of $10 per participant.  Administrative expenses
    charged by the third party administrator and all other expenses incurred in
    conjunction with the Plan are paid by the Company.  Investment advisory and
    management fees are allocated proportionately to Plan participants based on
    their respective account balances in certain funds.  Loan fees are charged
    directly to the participant's account against the investment option for
    which the loan was originally charged.

    Plan Termination - Although it has not expressed any intent to do so,
    Wausau-Mosinee Paper Corporation has the right under the Plan to terminate
    the Plan subject to the provisions of ERISA.  Upon termination of the Plan,
    all account balances of the participants become fully vested.  The account
    will be held under the Plan and continue to accrue investment earnings
    until all vested benefits have been distributed according to the terms of
    the Plan.

2.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

    Basis of Presentation - The accompanying financial statements have been
    prepared on the accrual basis of accounting in accordance with accounting
    principles generally accepted in the United States.

    Benefits - Benefits are recorded when distributed.  The amount of benefit
    payments requested in 2003 that were distributed in 2004 was $398,428.  All
    benefit payments requested in 2002 were distributed in 2002.

    Investment Valuation and Income Recognition - The Plan's various mutual
    fund and company stock investments are carried at fair value which
    represents the quoted market
                                       -6-
    values of the underlying investments on the last business day of the plan
    year including current income and investment expenses.  Investments in the
    M&I Stable Principal Fund are stated at contract value which approximates
    fair value.

    Loans are stated at estimated fair value and are deemed collectible.
    Securities transactions are accounted for on the trade-date basis (the date
    the order to buy or sell is executed).

    Gains or losses on security transactions are recorded as the difference
    between proceeds received and the carrying value of the investments.
    Interest income is recognized on the accrual method, and dividend income is
    recorded on the ex-dividend date.

    Net appreciation and depreciation in fair value of investments on the
    statements of changes in net assets available for benefits includes both
    unrealized appreciation or depreciation and realized gains and losses.
    Interest and dividends are identified separately.

    Use of Estimates - The preparation of financial statements in conformity
    with accounting principles generally accepted in the United States requires
    management to make estimates and assumptions that affect the reported
    amounts of net assets available for benefits and changes therein.  Actual
    results could differ from those estimates.  The Plan utilizes various
    investment instruments, including mutual funds and investment contracts.
    Investment securities are exposed to various risks including but not
    limited to, interest rate, market, and credit risks.  Due to the level of
    risk associated with certain investment securities, it is reasonably
    possible that changes in the value of investment securities will occur in
    the near term.

3.  INVESTMENTS

    The following represents a summary of the fair value of investments at
    December 31, 2003 and 2002.  Investments that individually represent 5% or
    more of the Plan's net assets available for benefits are separately
    identified.
                                       -7-




                                                                  ASSET FAIR VALUE
                                                                2003           2002
INVESTMENTS AT FAIR VALUE AS DETERMINED
  BY QUOTED MARKET PRICE
                                                                  
Common/collective trusts:
  Northern Capital Management Fund,
     2,935,084 and 2,995,358 shares, respectively         $ 32,122,882  $  26,592,928
  Wausau-Mosinee Common Stock Fund,
     492,480 and 619,086 shares, respectively                6,798,430      6,994,381

           Total common/collective trusts                   38,921,312     33,587,309

Pooled separate accounts                                     5,895,261      4,621,599

Registered investment companies:
  ABN AMRO/Chicago Capital Growth Fund,
    566,640 and 603,211 shares, respectively                12,449,076     10,900,025
  Brandywine Blue Chip Fund,
    482,722 and 477,972 shares, respectively                11,498,429      8,799,471
  Thompson Plumb Growth Fund,
     281,897 and 240,162 shares, respectively               12,936,266      8,384,066
  Vanguard 500 Admiral Fund,
     103,701 and 81,121 shares, respectively                10,648,008             --
  Other                                                     33,292,884     26,009,557

           Total registered investment companies            80,824,663     54,093,119

INVESTMENTS AT ESTIMATED VALUE

Participant loans                                            2,616,778      2,348,625

INVESTMENTS AT CONTRACT VALUE

Investment contracts between financial institutions -
  M&I Stable Principal Fund,
    40,650,648 and 40,226,287 shares, respectively          40,650,648     40,226,287

TOTAL INVESTMENTS                                        $ 168,908,662   $134,876,939

                                       -8-

    During 2003 and 2002, the Plan's investments (including investments bought,
    sold, and held during the year) appreciated (depreciated) in value as
    follows:


                                                                 NET CHANGE IN
                                                                  FAIR VALUE
                                                               2003            2002
      INVESTMENTS AT FAIR VALUE DETERMINED
      BY QUOTED MARKET PRICE:
                                                                   
      Common/collective trusts                            $  7,460,919   $  (9,023,058)
      Pooled separate accounts/investment contract           1,029,551        (644,032)
      Registered investment companies                       17,394,142     (15,008,362)
                                                          $ 25,884,612   $ (24,675,452)

1.  INVESTMENT CONTRACT

    In 2003 and 2002, the Plan maintained an investment contract with Marshall
    & Ilsley Trust Company ("M&I").  Contributions are maintained in a pooled
    account.  The account is credited with earnings on the underlying
    investments and charged for Plan withdrawals and administrative expenses
    charged by M&I.  The contract is included in the financial statements at
    contract value, which approximates fair value, as reported to the Plan by
    M&I.  Contract value represents contributions made under the contract plus
    earnings, less plan withdrawals and administrative expenses.  The average
    yield and crediting interest rates on the contract were 4.33% and 4.11%,
    respectively, for the year ended December 31, 2003 and 4.93% and 5.23% for
    the year ended December 31, 2002, respectively.  The basis and frequency of
    determining the crediting interest rate is done on a daily basis.  There
    were no guarantees or limitations on the contract at December 31, 2003 and
    2002.

5.  FEDERAL INCOME TAX STATUS

    The Internal Revenue Service has determined and informed the Company by a
    letter dated July 18, 2003, that the Plan is qualified and the trust
    established under the Plan is tax-exempt, under the appropriate sections of
    the IRC.

6.  RELATED PARTY TRANSACTIONS

    The Plan invests in Company common stock.  In addition, certain plan
    investments represent shares of mutual funds and collective trust funds
    managed by the Trustee.  These transactions are considered party-in-
    interest transactions.  These transactions are not, however, considered
    prohibited transactions under ERISA regulations.  Fees paid by the Plan for
    investment management services were included as a reduction of the return
    earned on each fund.
                                       -9-



WAUSAU-MOSINEE PAPER CORPORATION
SAVINGS & INVESTMENT PLAN

FORM 5500, SCHEDULE H, PART IV, LINE 4I - SCHEDULE OF ASSETS HELD FOR
INVESTMENTS PURPOSES
DECEMBER 31, 2003

                                           DESCRIPTION OF INVESTMENT
                                           INCLUDING MATURITY DATE,                  NUMBER
IDENTITY OF ISSUE, BORROWER,               RATE OF INTEREST, COLLATERAL,             OF SHARES/       FAIR
LESSOR OR SIMILAR PARTY                    PAR OR MATURITY VALUE                     PAR VALUE        VALUE
                                                                                         
Marshall & Ilsley Trust Company*           Common/collective trust
                                           - Northern Capital Management Fund        2,935,084    $32,122,882
Marshall & Ilsley Trust Company*           Common/collective trust
                                           - Wausau-Mosinee Common Stock Fund          492,480      6,798,430
Marshall & Ilsley Trust Company*           Pooled separate account
                                           - M&I Aggressive Balanced Portfolio Fund     52,288      1,248,499
Marshall & Ilsley Trust Company*           Pooled separate account
                                           - M&I Moderate Balanced Portfolio Fund      122,710      2,549,452
Marshall & Ilsley Trust Company            *Pooled separate account
                                           - M&I Diversified Stock Portfolio Fund       82,477      2,097,310
Marshall & Ilsley Trust Company            *Pooled separate account
                                           - M&I Stable Principal Fund              40,650,648     40,650,648
AIM Small Cap Growth Fund                  Registered investment company
                                           - AIM Small Cap Growth Fund                  31,343        805,821
Artisan International Fund                 Registered investment company
                                           - Artisan International Fund                425,783      8,051,563
Brandywine Blue Chip Fund                  Registered investment company
                                           - Bradywine Blue Chip Fund                  482,722     11,498,429
ABN AMRO/Chicago Capital                   Registered investment company
  Growth Fund                              - ABN AMRO/Chicago Capital Growth Fund      566,640     12,449,076
Fidelity Advisor Equity Income Fund        Registered investment company
                                           - Fidelity Advisor Equity Income Fund       152,228      3,935,092
MFS Mid Cap Growth Fund                    Registered investment company
                                           - MFS Mid Cap Growth Fund                   784,215      6,124,720
Marshall Mid Cap Value Fund                Registered investment company
                                           - Marshall Mid Cap Value Fund               187,204      2,585,282
Royce Opportunity Fund                     Registered investment company
                                           - Royce Opportunity Fund                    531,916      6,409,586
Thompson Plumb Balanced Fund               Registered investment company
                                           - Thompson Plumb Balanced Fund              289,136      5,380,820
Thompson Plumb Growth Fund                 Registered investment company
                                           - Thompson Plumb Growth Fund                281,897     12,936,266
Vanguard 500 Index Fund                    Registered investment company
                                           - Vanguard 500 Index Fund                   103,701     10,648,008
Participant Loans*                         Rate during year 4.0% - 10.5%             2,616,778     $2,616,778

Total assets (held at end of year)                                                 168,908,662   $168,908,662

* Party-in-interest.

                                       -10-

                                  SIGNATURES

      Pursuant to the requirements of the Securities Exchange Act of 1934, the
Plan administrator of the Wausau-Mosinee Paper Corporation Savings and
Investment Plan has duly caused this annual report to be signed on its behalf
by the undersigned hereunto duly authorized.


                                    WAUSAU-MOSINEE PAPER CORPORATION
                                    EMPLOYEE BENEFITS COMMITTEE



DATE: June 28, 2004                 By:    STUART R. CARLSON
                                           Stuart R. Carlson
                                           Chairman
                                       -11-

                                 EXHIBIT INDEX
                                      TO
                                   FORM 11-K
                                      OF
                       WAUSAU-MOSINEE PAPER CORPORATION
                          SAVINGS AND INVESTMENT PLAN
                     FOR THE YEAR ENDED DECEMBER 31, 2003
                 Pursuant to Section 102(d) of Regulation S-T
                        (17 C.F.R. Section 232.102(d))



Exhibit 23.1       Consent of Deloitte & Touche LLP
                                       -12-