Ameren Corporation is a Fortune 500 company with assets of $23 billion. It is the parent company of Ameren Illinois, based in Collinsville, Ill., and Ameren Missouri in St. Louis, Mo. Ameren was created by the merger of CIPSCO Incorporated and Union Electric Company. The name comes from combining the words American and Energy. Employing more than 8,500 personnel, Ameren companies serve 2.4 million electric customers and more than 900,000 natural gas customers across 64,000 square miles in Illinois and Missouri. 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 nearly 10,300 megawatts of electricity. Ameren's rates are some of the lowest in the nation.