Union Electric Company

Union Electric Company, operating as Ameren Missouri, is a rate-regulated electric and natural gas utility headquartered in St. Louis, Missouri. It was founded in 1881 and incorporated in 1922 as Union Electric Light and Power Company. Union Electric Company is a wholly-owned subsidiary of Ameren Corporation (NYSE: AEE), which is also based in St. Louis. As of March 2026, the company has approximately 3,830 employees and a trailing 12-month revenue of $4.77 billion. Ameren Corporation as a whole employs around 9,000 people and serves 2.5 million electric and over 900,000 natural gas customers across 67,700 square miles in Illinois and Missouri.

Union Electric Company (Ameren Missouri) provides electric and natural gas services across a 24,000 square-mile area in central and eastern Missouri, including the greater St. Louis area. The company generates electricity using a diverse mix of sources, including coal, nuclear, natural gas, hydroelectric, methane gas, and solar energy. They supply electric services to approximately 1.2 million customers and natural gas services to roughly 0.1 million customers. The company also historically operated district steam plants.

Union Electric Company's patent litigation posture indicates it is an operating company defending its interests rather than a patent assertion entity. The company has been involved in two tracked cases, both as a plaintiff before the Patent Trial and Appeal Board (PTAB). These cases are Union Electric Company v. Birchtech Corp. (filed 2025-07-18) and Union Electric Company v. Birchtech Corporation. The specific details of these cases suggest an active defense or challenge concerning patent validity.

The company's history includes significant involvement in utility development in Missouri, such as building the Ashley Street Plant in 1904 and completing the Bagnell Dam in 1929, which created the Lake of the Ozarks. Union Electric Company was publicly traded on the NYSE under the ticker UEP until its merger with CIPSCO Inc. in 1997, which formed Ameren Corporation.