- The Red River (French: rivière Rouge), also called the Red River of the North (French: rivière Rouge du Nord) to differentiate it from the Red River in the south of the continent, is a river in the north-central United States and the Canadian Prairies. Originating at the confluence of the Bois de Sioux and Otter Tail rivers between the U.S. states of Minnesota and North Dakota, it flows northward through the Red River Valley, forming most of the border of Minnesota and North Dakota and continuing into Manitoba. It empties into Lake Winnipeg, whose waters join the Nelson River and ultimately flow into Hudson Bay.