Ameren Corp. named Mark Birk as president and chairman of Ameren Missouri, effective Jan. 1. He replaces Marty Lyons, who on Jan. 1 will ascend to CEO of Ameren Corp. At the same time, current Ameren Corp. CEO Warner Baxter will become the company's executive chairman. Birk, a 35-year veteran of the company, since 2017 has served as senior vice president for customer and power operations. He oversees engineering, construction, operations and maintenance of Ameren Missouri's electric and natural gas distribution systems and non-nuclear generation and energy management, as well as customer experience operations for more than 1 million electric and natural gas customers.