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 include:

2010
Ameren subsidiaries Illinois Power, CIPS and Cilco merge into Ameren Illinois, while AmerenUE changes its name to Ameren Missouri. Ameren Transmission Company is formed.

2004
Ameren acquires Illinois Power.
 
2003
Ameren acquires CILCORP Inc.

1997
Union Electric and CIPSCO, Inc. merge to create Ameren Corporation.

1984
Union Electric produces nuclear energy for the first time when the Callaway Plant begins generating 1,143 megawatts of power.

1952
CIPSCO joins with Illinois Power and Union Electric to form the Midwest Power Pool system.
 
1931
“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.
 
1904
Union Company “electrifies” the St. Louis World Fair - the nation’s first broad-scale demonstration of power.
        
1902
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.
history, ameren, union electric, CIPSCO, CILCORP, Cilco, Illinois Power, AmerenUE, century
 
 
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