POWER OF ATTORNEY
                                -----------------

     WHEREAS,  directors,  certain officers,  and beneficial owners of more than
10% of any equity security of AMEREN CORPORATION, a Missouri corporation (herein
referred to as the  "Company"),  as well as certain  directors  and  officers of
Company  subsidiaries,  are  required to file with the  Securities  and Exchange
Commission and the New York Stock  Exchange,  under Section 16 of the Securities
Exchange  Act of  1934,  as now  and  hereafter  amended,  statements  regarding
ownership  and change in  ownership  of equity  securities  of the Company  (the
"Reporting Forms"); and

     WHEREAS,  the undersigned  holds an office or offices in the Company and/or
Company subsidiaries and is required to file such Reporting Forms.

     NOW,  THEREFORE,  the undersigned hereby constitutes and appoints Steven R.
Sullivan  and/or Ronald K. Evans and/or G. L. Waters and/or any  individual  who
hereafter  holds the offices of Secretary or Assistant  Secretary of the Company
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
(including,  without  limitation,  any  electronic  signature) to said Reporting
Forms 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.  The undersigned  acknowledges that the foregoing  attorney-in-fact,  in
serving in such  capacity at the request of the  undersigned,  are not assuming,
nor is the Company assuming, any of the undersigned's responsibilities to comply
with Section 16 of the Securities  Exchange Act of 1934. The undersigned further
acknowledges  that in whatever  capacities he/she may hold in the Company and/or
its  subsidiaries  in the future,  this Power of Attorney  shall  remain in full
force and effect until such time it would be revoked by the undersigned.

     IN WITNESS WHEREOF,  the undersigned has hereunto set his/her hand this 2nd
day of September, 2004:

                                               /s/ Mark C. Birk
                                       ---------------------------------
                                                   Mark C. Birk

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

     On this 2nd day of  September,  2004,  before  me, the  undersigned  Notary
Public in and for said State,  personally  appeared Mark C. Birk, known to me to
be the person  described in and who executed the foregoing power of attorney and
acknowledged  to me that he/she  executed  the same as his/her free act and deed
for the purposes therein stated.

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


                                                /s/ S. A. Kitchens
                                       ------------------------------------
                                                    S. A. Kichens
                                              Notary Public - Notary Seal
                                                  STATE OF MISSOURI
                                                  St. Louis County
                                        My Commission Expires: July 9, 2007