Ameren Corp. provides electric and natural gas services. The company operates its business through three segments: Ameren Missouri, Ameren Illinois, and Merchant Generation. The Ameren Missouri segment operates a rate-regulated electric generation, transmission and distribution business, and a rate-regulated natural gas transmission and distribution business in Missouri. The Ameren Illinois segment operates a rate-regulated electric and natural gas transmission and distribution business in Illinois. The Merchant Generation segment for Ameren consists primarily of the operations or activities of AER, including Genco, EEI, AERG, and Marketing company. Ameren was founded in 1997 and is headquartered in St. Louis, MO.