Brand Description Back  
St. Louis-based Ameren Corporation (NYSE: AEE) is among the nation's largest investor-owned electric and gas utilities. The largest electric utility in Missouri and the second largest in Illinois, Ameren companies provide energy services to electric and natural gas customers throughout its territory.

Created by the year-end 1997 merger of Union Electric Company and CIPSCO, parent of Central Illinois Public Service Company, the company grew in 2003 with the acquisition of CILCORP, the parent of Central Illinois Light Company and again in 2004 with the acquisition of Illinois Power Company.