Ameren Corp. operates as a public utility holding company that provides electric and natural gas services. It operates through the following business segments: Ameren Missouri, Ameren Illinois Electric Distribution, Ameren Illinois Natural Gas, and Ameren Transmission. The Ameren Missouri segment includes all of the operations of Ameren Missouri. The Ameren Illinois Electric Distribution segment consists of the electric distribution business of Ameren Illinois. The Ameren Illinois Natural Gas segment consists of the natural gas business of Ameren Illinois. The Ameren Transmission segment primarily consists of the aggregated electric transmission businesses of Ameren Illinois and ATXI. The company was founded in 1902 and is headquartered in St. Louis, MO.