Exhibit 21

SUBSIDIARIES OF AMEREN CORPORATION

AT DECEMBER 31, 2005



|                                                 |  |                                      
|------------------------------------------------ |  | -------------------------------------
|Name                                             |  | State or Jurisdiction ofIncorporation
|Ameren Corporation                               |  | Missouri                             
|Ameren Development Company                       |  | Missouri                             
|Ameren Energy Communications, Inc.               |  | Missouri                             
|Ameren ERC, Inc.                                 |  | Missouri                             
|Missouri Central Railroad Company                |  | Delaware                             
|Gateway Energy Systems, L.C.                     |  | Missouri                             
|Gateway Energy WGK Project, L.L.C.               |  | Missouri                             
|Ameren Energy, Inc.                              |  | Missouri                             
|Ameren Energy Resources Company                  |  | Illinois                             
|Ameren Energy Development Company                |  | Illinois                             
|Ameren Energy Generating Company                 |  | Illinois                             
|Coffeen and Western Railroad Company             |  | Illinois                             
|Ameren Energy Marketing Company                  |  | Illinois                             
|Illinois Materials Supply Co.                    |  | Illinois                             
|Electric Energy, Inc. (40% interest)             |  | Illinois                             
|Midwest Electric Power Inc.                      |  | Illinois                             
|Joppa and Eastern Railroad Company               |  | Illinois                             
|Met South, Inc.                                  |  | Illinois                             
|Massac Enterprises LLC                           |  | Illinois                             
|Joppa Generating Station LLC                     |  | Illinois                             
|Southern Materials Transfer, Inc.                |  | Illinois                             
|AmerenEnergy Medina Valley Cogen, (No. 4) L.L.C. |  | Illinois                             
|AmerenEnergy Medina Valley Operations, L.L.C.    |  | Illinois                             
|AmerenEnergy Medina Valley Cogen (No. 2) L.L.C.  |  | Illinois                             
|AmerenEnergy Medina Valley Cogen, L.L.C.         |  | Illinois                             
|Ameren Energy Fuels and Services Company         |  | Illinois                             
|Cowboy Railroad Development Co.                  |  | Arkansas                             
|AFS Development Company, LLC                     |  | Illinois                             
|Gateway Terminal LLC                             |  | Missouri                             
|CLM LLC - VII                                    |  | Delaware                             
|CLM LLC - VIII                                   |  | Delaware                             
|CILCORP Lease Management LLC                     |  | Delaware                             
|Ameren Services Company                          |  | Missouri                             
|Central Illinois Public Service Company          |  | Illinois                             
|CIPS Energy Inc.                                 |  | Illinois                             
|CIPSCO Investment Company                        |  | Illinois                             
|CIPSCO Securities Company                        |  | Illinois                             
|CIPSCO Leasing Company                           |  | Illinois                             
|CLC Aircraft Leasing Company                     |  | Illinois                             
|CLC Leasing Company A                            |  | Illinois                             
|CIPSCO Energy Company                            |  | Illinois                             
|CEC-ACLP Co.                                     |  | Illinois                             
|CIPSCO Ventures Company                          |  | Illinois                             



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SUBSIDIARIES OF AMEREN CORPORATION

AT DECEMBER 31, 2005



|                                                        |  |                                      
|------------------------------------------------------- |  | -------------------------------------
|Name                                                    |  | State or Jurisdiction ofIncorporation
|Union Electric Company                                  |  | Missouri                             
|Union Electric Development Corporation                  |  | Missouri                             
|Electric Energy, Inc. (40% interest)                    |  | Illinois                             
|Midwest Electric Power Inc.                             |  | Illinois                             
|Joppa and Eastern Railroad Company                      |  | Illinois                             
|Met South, Inc.                                         |  | Illinois                             
|Massac Enterprises LLC                                  |  | Illinois                             
|Joppa Generating Station LLC                            |  | Illinois                             
|Southern Materials Transfer, Inc.                       |  | Illinois                             
|CILCORP INC.                                            |  | Illinois                             
|Central Illinois Light Company                          |  | Illinois                             
|CILCO Exploration and Development Co.                   |  | Illinois                             
|AmerenEnergy Resources Generating Company               |  | Illinois                             
|CIM Leasing LLC                                         |  | Delaware                             
|CILCO Energy Corporation                                |  | Illinois                             
|CIM Energy Investments Inc.                             |  | Illinois                             
|QST Enterprises Inc.                                    |  | Illinois                             
|QST Energy Inc.                                         |  | Illinois                             
|QST Energy Trading Inc.                                 |  | Illinois                             
|CILCORP Infraservices Inc.                              |  | Illinois                             
|QST Inc.                                                |  | Illinois                             
|ESE Land Corporation                                    |  | Illinois                             
|Savannah Resources Corp.                                |  | California                           
|ESE Placentia Development Corporation                   |  | Illinois                             
|California/Nevada Development L.L.C.                    |  | Delaware                             
|CILCORP Ventures Inc.                                   |  | Illinois                             
|CILCORP Energy Services Inc.                            |  | Illinois                             
|Agricultural Research & Development Corp.               |  | Illinois                             
|Peoria Medical Research Corp.                           |  | Illinois                             
|Illinois Power Company                                  |  | Illinois                             
|IP Gas Supply Company                                   |  | Illinois                             
|Illinois Power Transmission Company, LLC                |  | Delaware                             
|Illinois Power Securitization Limited Liability Company |  | Delaware                             
|Illinois Power Special Purpose Trust                    |  | Delaware                             
|Illinois Power Financing I                              |  | Delaware                             
|Illinois Power Financing II                             |  | Delaware