is a holding company formed from the 1998 merger of Interstate Power, IES Utilities (holding company was IES Industries), and Wisconsin Power & Light (holding company was WPL Holdings). Effective January 2002, Interstate Power & IES Utilities merged into one utility, Interstate Power and Light Company. IES Utilities was formed from the 1993 merger of Iowa Electric Light & Power and Iowa Southern Utilities.

Alliant Energy Corporation is a public utility holding company that incorporated in Madison, Wisconsin in 1981.