Missouri River and Lake Oahe in South Dakota, USA44.8N 100.6W
This image shows the Missouri River flowing through the state of South Dakota, USA. It is the longest river in North America and a major waterway of the central United States. Rising in the Rocky Mountains of western Montana, the Missouri flows east and south for 2,341 miles (3,767 km) before entering the Mississippi River north of St. Louis, Missouri. The river takes drainage from a sparsely populated, semi-arid watershed of more than half a million square miles (1,300,000 km2), which includes parts of ten U.S. states and two Canadian provinces.
The particularly wide section of the river in the upper left quadrant is Lake Oahe, a large reservoir behind the Oahe Dam on the Missouri River beginning in central South Dakota and continuing north into North Dakota in the United States. The lake has an area of 370,000 acres (1,500 km2) and a maximum depth of 205 ft (62 m). By volume, it is the fourth-largest reservoir in the US. Lake Oahe has a length of approximately 231 mi (372 km) and has a shoreline of 2,250 mi (3,620 km).