<PAGE>
                                                                    EXHIBIT 24.1

                                POWER OF ATTORNEY

         WHEREAS, CILCORP INC., an Illinois corporation (herein referred to as
the "Company"), is required to file with the Securities and Exchange Commission,
under the provisions of the Securities Exchange Act of 1934, as amended, its
annual report on Form 10-K for the year ended December 31, 2002; and

         WHEREAS, each of the below undersigned holds the office or offices in
the Company set opposite his name;

         NOW, THEREFORE, each of the undersigned hereby constitutes and appoints
Gary L. Rainwater and/or Warner L. Baxter and/or Steven R. Sullivan the true and
lawful attorneys-in-fact of the undersigned, for and in the name, place and
stead of the undersigned, to affix the name of the undersigned to said Form 10-K
and any amendments thereto, and, for the performance of the same acts, each with
power to appoint in their place and stead and as their substitute, one or more
attorneys-in-fact for the undersigned, with full power of revocation; hereby
ratifying and confirming all that said attorneys-in-fact may do by virtue
hereof.

         IN WITNESS WHEREOF, the undersigned have hereunto set their hands this
14th day of March 2003:

Charles W. Mueller, Chairman and Director        /s/ Charles W. Mueller
                                                 -------------------------------

Gary L. Rainwater, President, Chief
       Executive Officer and Director
       (Principal Executive Officer)
                                                 -------------------------------

Paul A. Agathen, Director
                                                 -------------------------------

Warner L. Baxter, Senior Vice
       President and Director
       (Principal Financial Officer)
                                                 -------------------------------

Richard A. Liddy, Director                       /s/ Richard A. Liddy
                                                 -------------------------------

Richard A. Lumpkin, Director                     /s/ Richard A. Lumpkin
                                                 -------------------------------

Paul L. Miller, Jr., Director                    /s/ Paul L. Miller, Jr.
                                                 -------------------------------

Harvey Saligman, Director                        /s/ Harvey Saligman
                                                 -------------------------------

Thomas R. Voss, Director
                                                 -------------------------------

David A. Whiteley, Director
                                                 -------------------------------

James W. Wogsland, Director                      /s/ James W. Wogsland
                                                 -------------------------------

Martin J. Lyons, Vice President
       and Controller
       (Principal Accounting Officer)
                                                 -------------------------------



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STATE OF MISSOURI        )
                         )  SS.
CITY OF ST. LOUIS        )

         On this 14th day of March, 2003, before me, the undersigned Notary
Public in and for said State, personally appeared the above-named officers and
directors of Ameren Corporation, known to me to be the persons described in and
who executed the foregoing power of attorney and acknowledged to me that they
executed the same as their free act and deed for the purposes therein stated.

         IN TESTIMONY WHEREOF, I have hereunto set my hand and affixed my
official seal.


                                                     /s/ K. A. Bell
                                         ---------------------------------------
                                                       K. A. BELL
                                               Notary Public - Notary Seal
                                                   STATE OF MISSOURI
                                                   St. Louis County
                                         My Commission Expires: October 13, 2006