The James River (also known as the Jim River or the Dakota River) is a tributary of the Missouri River, approximately 710 miles (1,140 km) long, draining an area of 20,653 square miles (53,490 km2) in the U.S. states of North Dakota and South Dakota. About 70 percent of the drainage area is in South Dakota. The river provides the main drainage of the flat lowland area of the Dakotas between the two plateau regions known as the Coteau du Missouri and the Coteau des Prairies. This narrow area was formed by the James lobe of the Laurentide Ice Sheet during the last ice age, and as a consequence the watershed of the river is slender and it has few major tributaries for a river of its length.