洪水調節
Economic stability returned with the U.S. entry into World War II in 1941, when demand for the state's agricultural and industrial products grew as the nation mobilized for war. In 1944, the Pick–Sloan Plan was passed as part of the Flood Control Act of 1944 by the U.S. Congress, resulting in the construction of six large dams on the Missouri River, four of which are at least partially in South Dakota. Flood control, hydroelectricity, and recreational opportunities such as boating and fishing are provided by the dams and their reservoirs.