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, 2004

                                      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 PAPER CORP. 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
                          SAVINGS AND INVESTMENT PLAN
         (Former name or former address, if changed from last report)


                              WAUSAU PAPER CORP.
                                100 PAPER PLACE
                            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
                            1244 KRONENWETTER DRIVE
                            MOSINEE, WI 54455-9099
         (Former name or former address, if changed from last report)

                       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, 2004 and 2003                                 2

 Statements of Changes in Net Assets Available for Benefits for the  
     Years Ended December 31, 2004 and 2003                                 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, 2004                                         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, 2004 and 2003, 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. The Plan is not
required to have, nor were we engaged to perform, an audit of its internal
control over financial reporting. Our audits included consideration of internal
control over financial reporting as a basis for designing audit procedures that
are appropriate in the circumstances, but not for the purpose of expressing an
opinion on the effectiveness of the Company's internal control over financial
reporting. Accordingly, we express no such opinion. An audit also includes
examining, on a test basis, evidence supporting the amounts and disclosures in
the financial statements, 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,
2004 and 2003, 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 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

Milwaukee, Wisconsin
June 13, 2005
                                       -1-

WAUSAU-MOSINEE PAPER CORPORATION
SAVINGS AND INVESTMENT PLAN


STATEMENTS OF NET ASSETS AVAILABLE FOR BENEFITS
DECEMBER 31, 2004 AND 2003


                                                         2004           2003
                                                           
ASSETS:
 Cash and cash equivalents                         $       386   $    177,634
 Investments                                        184,272,282   168,908,662

 Receivables:
  Employer                                               41,283        92,899
  Participants                                          149,693       180,512
  Accrued income                                        143,116       137,169
  Other receivables                                      52,066        57,908

      Total receivables                                 386,158       468,488

NET ASSETS AVAILABLE FOR BENEFITS                  $184,658,826  $169,554,784


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, 2004 AND 2003

                                                         2004           2003
                                                             
ADDITIONS:
  Net appreciation in fair value of investments      $12,450,482    $25,884,612
  Contributions:
    Employer                                           2,680,369      2,622,928
    Participants                                      10,151,551      9,987,650
    Participant rollovers                                257,604        135,796

           Total contributions                        13,089,524     12,746,374

  Interest income                                      1,764,251      1,893,960
  Dividend income                                        532,798        363,554

           Total additions                            27,837,055     40,888,500

DEDUCTIONS:
  Benefits paid to participants                       12,644,529      6,394,359
  Administrative expenses                                 88,484         94,837

           Total deductions                           12,733,013      6,489,196

NET INCREASE                                          15,104,042     34,399,304

NET ASSETS AVAILABLE FOR BENEFITS:
  Beginning of year                                  169,554,784    135,155,480

  End of year                                       $184,658,826   $169,554,784

See notes to financial statements.
                                       -3-

WAUSAU-MOSINEE PAPER CORPORATION
SAVINGS AND INVESTMENT PLAN 

NOTES TO FINANCIAL STATEMENTS
YEARS ENDED DECEMBER 31, 2004 AND 2003

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, subject to
    certain statutory 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, 2004
    and 2003.
                                       -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
    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, 2004 and 2003 was $444,868 and $369,456, respectively.

    PARTICIPANT LOANS-Participants may borrow from their accounts. Loan
    transactions are treated as a segregated investment of the participant's
    accounts. 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-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. 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 2004 that were distributed in 2005 was $220,646. The
    amount of benefit payments requested in 2003 that were distributed in 2004
    was $398,428.

    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 values of the underlying investments on the last business
    day of the plan year including
                                       -6-
    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 of America
    requires Plan 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, 2004 and 2003. Investments that individually represent 5% or
    more of the Plan's net assets available for benefits are separately
    identified.
                                       -7-



                                                            ASSET FAIR VALUE
                                                           2004           2003
INVESTMENTS AT FAIR VALUE AS DETERMINED 
  BY QUOTED MARKET PRICE
                                                                 
Common/collective trust:
  Northern Capital Management Fund, 
    2,676,430 and 2,935,084 shares, respectively         $30,247,155    $32,122,882

Employer Common Stock*                                     6,815,792      6,798,430

Pooled separate accounts                                   6,938,772      5,895,261

Registered investment companies:
  ABN AMRO Growth Fund,
    527,523 and 566,640 shares, respectively              12,206,891     12,449,076
  Brandywine Blue Chip Fund,
    471,776 and 482,722 shares, respectively              13,403,154     11,498,429
  Thompson Plumb Growth Fund,
    296,875 and 281,897 shares, respectively              13,890,762     12,936,266
  Vanguard 500 Index Fund,
    111,245 and 103,701 shares, respectively              12,419,415     10,648,008
  Artisan International Fund,
    458,127 and 425,783 shares, respectively              10,142,926      8,051,563
  Royce Opportunity Fund,
    728,223 and 531,916 shares, respectively               9,590,695      6,409,586
  Other                                                   23,022,157     18,831,735

           Total registered investment companies          94,676,000     80,824,663

INVESTMENTS AT ESTIMATED VALUE

Participant loans*                                         2,921,610      2,616,778

INVESTMENTS AT CONTRACT VALUE

Investment contracts between financial institutions -
  M&I Stable Principal Fund,*
    42,672,953 and 40,650,648 shares, respectively        42,672,953     40,650,648

TOTAL INVESTMENTS                                       $184,272,282   $168,908,662

*Party-in-interest

                                       -8-



    During 2004 and 2003, the Plan's investments (including investments bought,
    sold, and held during the year) appreciated in value as follows:

                                                            NET CHANGE IN
                                                             FAIR VALUE
                                                          2004         2003
                                                             
    INVESTMENTS AT FAIR VALUE DETERMINED
      BY QUOTED MARKET PRICE:
      Common/collective trusts                       $   980,221   $ 6,073,399
      Employer Common Stock                            1,789,982     1,387,520
      Pooled separate accounts/investment contract       572,874     1,029,551
      Registered investment companies                  9,107,405    17,394,142
    
                                                     $12,450,482   $25,884,612

4.  INVESTMENT CONTRACT

    In 2004 and 2003, 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 4.01% and 3.91%,
    respectively, for the year ended December 31, 2004 and 4.33% and 4.11% for
    the year ended December 31, 2003, 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, 2004 and
    2003.

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 AT END OF
YEAR)
DECEMBER 31, 2004

                                     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        2,676,430    $30,247,155
Marshall & Ilsley Trust Company*     Employer Common Stock
                                     - Wausau-Mosinee Common Stock Fund          372,040      6,815,792
Marshall & Ilsley Trust Company*     Pooled separate account
                                     - M&I Aggressive Balanced Portfolio Fund     61,280      1,618,379
Marshall & Ilsley Trust Company*     Pooled separate account
                                     - M&I Moderate Balanced Portfolio Fund      132,696      2,958,922
Marshall & Ilsley Trust Company*     Pooled separate account
                                     - M&I Diversified Stock Portfolio Fund       83,043      2,361,471
Marshall & Ilsley Trust Company*     Pooled separate account
                                     - M&I Stable Principal Fund              42,672,953     42,672,953
AIM Small Cap Growth Fund            Registered investment company 
                                     - AIM Small Cap Growth Fund                  35,059        962,721
Artisan International Fund           Registered investment company
                                     - Artisan International Fund                458,127     10,142,926
Brandywine Blue Chip Fund            Registered investment company
                                     - Bradywine Blue Chip Fund                  471,776     13,403,154
ABN AMRO Growth Fund                 Registered investment company
                                     - ABN AMRO Growth Fund                      527,523     12,206,891
Fidelity Advisor Equity Income Fund  Registered investment company
                                     - Fidelity Advisor Equity Income Fund       156,217      4,425,629
MFS Mid Cap Growth Fund              Registered investment company
                                     - MFS Mid Cap Growth Fund                   803,367      7,182,098
Marshall Mid Cap Value Fund*         Registered investment company
                                     - Marshall Mid Cap Value Fund               327,394      4,930,552
Royce Opportunity Fund               Registered investment company
                                     - Royce Opportunity Fund                    728,223      9,590,695
Dreyfus Premier Balanced Opp Fund    Registered investment company
                                     - Dreyfus Premier Balanced Opp Fund         281,836      5,521,157
Thompson Plumb Growth Fund           Registered investment company
                                     - Thompson Plumb Growth Fund                296,875     13,890,762
Vanguard 500 Index Fund              Registered investment company
                                     - Vanguard 500 Index Fund                   111,245     12,419,415
Participant Loans*                   Rate during year 4.0% - 10.5%             2,921,610      2,921,610

Total assets (held at end of year)                                                         $184,272,282

* 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 29, 2005                 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, 2004
                 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-