Ameren Corporation is a Fortune 500 company that trades on the New York Stock Exchange under the symbol AEE. It is the parent company of Ameren Illinois, based in Collinsville, Ill., and Ameren Missouri in St. Louis. Ameren Transmission Company of Illinois (ATXI), also based in St. Louis, designs and builds regional transmission projects. Ameren was created by the combination of three Illinois utilities (CIPSCO Incorporated, CILCO Inc. and Illinois Power Company) and Union Electric Company of St. Louis. The name comes from combining the words American and Energy.

Employing approximately 9,000 personnel, Ameren powers the quality of life for 2.5 million electric customers and more than 900,000 natural gas customers across a 64,000-square-mile area. Ameren Missouri ranks as the largest electric power provider in Missouri, and Ameren Illinois ranks as Illinois' third largest natural gas distribution operation in total number of customers.

Ameren companies generate a net capacity of approximately 9,300 megawatts of electricity and own over 8,000 transmission miles across its operating companies and a variety of energy markets. Ameren's rates are some of the lowest in the nation.

Ameren employees, totaling approximately 9,370, provide energy services to approximately 2.4 million electric customers and more than 900,000 natural gas customers across 64,000 square miles in Illinois and Missouri.