Lake Sakakawea is a reservoir in the north central United States, located in the Missouri River basin in central North Dakota. Named for the Shoshone-Hidatsa woman Sakakawea, it is the largest man-made lake in North Dakota and the third largest in the United States, after Lake Mead and Lake Powell. The lake lies in parts of six counties in western North Dakota: Dunn, McKenzie, McLean, Mercer, Mountrail, and Williams.