Alliant Energy Corporation is a public utility holding company headquartered in Madison, Wisconsin, providing power in Iowa and Wisconsin.
History
Interstate Power and Light Company (IPL) expanded greatly in the late 1920s to include operations in Iowa, Wisconsin, Minnesota, North and South Dakota, Nebraska, Oklahoma, and Manitoba (Canada). One of the largest purchases in the late 1920s was the purchase of what became its northern Minnesota territory from the Wilbur Foshay interests.
In the 1930s and 1940s, the effects of the Depression and passage of laws to regulate utility operations at the state and federal level had an effect on IPC as well as its neighbors. In Iowa, the legislature passed laws making it easier for cities to establish municipal utilities (and indeed, there are over 100 municipal utilities in Iowa today). By 1940, the state of Nebraska had passed laws that forced all investor-owned utilities in that state to sell their operations to one of several "public power districts" operating in that state.
During the 1940s, IPC divested itself of all its operations that were not part of its main territory in southern MN / northern Iowa. The largest chunk of territory was that operating in northeast ND / northern MN / Emerson, Manitoba which was sold in summer 1943 and fall 1944. The SD properties (around Winner) were sold in 1946. It would not be until 1956 when the last isolated district — the area around Waconia, MN — was sold to Northern States Power.
As IPC sold its properties that were isolated from the main system, it picked up others that were adjacent to its system and more easily interconnected: the Eastern Iowa Power system, and the Iowa / Minnesota properties of the Central States Power and Light Corporation.