The Saint Louis River (abbreviated St. Louis River) is a river in the U.S. states of Minnesota and Wisconsin that flows into Lake Superior. The largest U.S. river to flow into the lake, it is 192 miles (309 km) in length and starts 13 miles (21 km) east of Hoyt Lakes, Minnesota. The river's watershed covers 3,634 square miles (9,410 km2). Near the Twin Ports of Duluth, Minnesota and Superior, Wisconsin, the river becomes a freshwater estuary. The lower St. Louis is the only river in the state with whitewater rafting opportunities.