<P> The St. Croix River (French: Holy Cross) is a tributary of the Mississippi River, approximately 169 miles (272 km) long, in the U.S. states of Wisconsin and Minnesota . The lower 125 miles (201 km) of the river form the border between Wisconsin and Minnesota . The river is a National Scenic Riverway under the protection of the National Park Service . A hydroelectric plant at St. Croix Falls supplies power to the Minneapolis--St. Paul metropolitan area . </P> <P> The St. Croix River rises in the northwestern corner of Wisconsin, out of Upper St. Croix Lake in Douglas County, near Solon Springs, approximately 20 miles (32 km) south of Lake Superior . It flows south to Gordon, then southwest . It is joined by the Namekagon River in northern Burnett County, where it becomes significantly wider . A few miles downstream the St. Croix meets the boundary between Minnesota and Wisconsin, which it demarcates for another 130 miles (209 km) until its confluence with the Mississippi River . </P> <P> Other major tributaries include the Kettle River, Snake River, and Sunrise River joining from the west, and the Apple River, Willow River, and Kinnickinnic River joining from the east . Just below Stillwater, Minnesota the river widens into Lake St. Croix, and eventually joins the Mississippi River at Prescott, Wisconsin, approximately 20 miles (32 km) southeast of St. Paul, Minnesota . </P> <P> The St. Croix River was one of the original eight rivers to have significant portions placed under protection by the National Wild and Scenic Rivers Act of 1968 . The upper reaches of the river in Wisconsin below the St. Croix Flowage, 15 miles (24 km) downstream from its source, as well as the Namekagon River, are protected as the St. Croix National Scenic Riverway . The free - flowing nature of the river is interrupted only by a hydroelectric dam operated by the Northern States Power Company at St. Croix Falls, Wisconsin . </P>

Where does the st croix river meet the mississippi