Company History

More than 100 years of strength

Ameren Corporation was formed in 1997 by the merger of Missouri’s Union Electric Company with neighboring Central Illinois Public Service Company - but our roots stretch back to 1902. We’re proud of our long, successful tradition of financial strength, low rates and pride in customer service.
Key dates in our century-long history includes:

Ameren subsidiaries Illinois Power, CIPS and Cilco merge into Ameren Illinois, while AmerenUE changes its name to Ameren Missouri. Ameren Transmission Company is formed.

Ameren acquires Illinois Power.
Ameren acquires CILCORP Inc.

Union Electric and CIPSCO, Inc. merge to create Ameren Corporation.

Union Electric produces nuclear energy for the first time when the Callaway Plant begins generating 1,143 megawatts of power.

CIPSCO joins with Illinois Power and Union Electric to form the Midwest Power Pool system.
“Bagnell Damming” the Osage River is successful, generating almost 175 megawatts of hydroelectricity at Union Electric’s Osage Plant and creating the popular Lake of the Ozarks.
Union Company “electrifies” the St. Louis World Fair - the nation’s first broad-scale demonstration of power.
Union Company (later Union Electric) is formed in St. Louis, Mo., and Central Illinois Public Service Company (later CIPSCO) begins life as the Mattoon City Railway Streetcar.
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