AmerenUE, formerly Union Electric Company, is a subsidiary of St. Louis-based Ameren Corp. that serves 2.3 million electric customers and 900,000 natural gas customers in a 64,000-square-mile area of Missouri and Illinois. The utility recently purchased a 33,422 square-feet office building located at 3700 S. Lindbergh Blvd in Sunset Hills, MO for $3,900,000 at $116.69 per square-feet.