Alliant Energy Corporation operates as a regulated investor-owned public utility holding company. Its primary focus is to provide regulated electric and natural gas service to its customers in the Midwest through its two public utility subsidiaries: Interstate Power and Light Company (IPL) and Wisconsin Power and Light Company (WPL). Its non-utility holdings are organized under Alliant Energy Finance, LLC. Its segments include IPL and WPL. IPL is a public utility engaged principally in the generation and distribution of electricity and the distribution and transportation of natural gas to retail customers in select markets in Iowa. WPL is a public utility engaged principally in the generation and distribution of electricity and the distribution and transportation of natural gas to retail customers in select markets in Wisconsin. WPL operates in municipalities pursuant to permits of indefinite duration and state statutes authorizing utility operation in areas annexed by a municipality.