Ameren
![A large section of the Taum Sauk upper reservoir failed, draining over a billion gallons of water in less than half an hour.](/Images/godic/202412/20/Taum_Sauk_reservoir-FERC_12-22-05_010744.jpg")
Ameren Corporation was created December 31, 1997 by the merger of Missouri's Union Electric Company (formerly NYSE: UEP) and the neighboring Central Illinois Public Service Company (CIPSCO Inc. holding, formerly NYSE: CIP). It is now a holding company for several power companies and energy companies. The company is based in St. Louis, Missouri, serving 2.4 million electric, and 900,000 natural gas customers across 64,000 square miles