Lake Oahe (oh-WAH'-hee) is a large reservoir behind Oahe Dam on the Missouri River; it begins in central South Dakota and continues 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). 51 recreation areas are located along Lake Oahe, and 1.5 million people visit the reservoir every year.