Minnesota (river)

Minnesota (river), river located in northeastern South Dakota and in Minnesota. A major tributary of the Mississippi River, it is generally considered to rise in Big Stone Lake on the border between Minnesota and South Dakota. It then enters Minnesota and flows in a southeastern direction to Mankato, where it turns north and joins the Mississippi River south of Saint Paul. The river flows through a wide valley originally cut by the River Warren, an ancient outlet of Lake Agassiz, a prehistoric glacial lake. Once known as Saint Peter or Saint Pierre, the Minnesota served as an important route for explorers and fur traders. The length of the river is 534 km (332 mi).