Ameren Corp. is a public utility holding company, which engages in the provision of electric and natural gas services. It operates through the following segments: Ameren Missouri, Ameren Illinois Electric Distribution, Ameren Illinois Natural Gas, Ameren Transmission, and Other. The Ameren Transmission segment consists of the aggregated electric transmission businesses of Ameren Illinois and Ameren Transmission Company of Illinois (ATXI). The company was founded in 1902 and is headquartered in St. Louis, MO.