Ameren Illinois is a regulated electric and natural gas utility that delivers energy to 1.2 million electric and 812,000 natural gas customers in central and southern Illinois. Headquartered in Collinsville, the Ameren Illinois service territory includes more than 1,200 communities and covers approximately 43,700 square miles. The company's complex energy delivery system is comprised of 4,500 miles of electric transmission lines, 45,400 miles of distribution lines, 18,000 miles of natural gas transmission and distribution mains, and 12 underground natural gas storage fields.