Lake Oahe Pierre, South Dakota and extends nearly as far north as Bismarck, North Dakota. Mobridge, South Dakota is located on the eastern shore of the central portion of the lake. Bridges over Lake Oahe include US Route 212 west of Gettysburg, South Dakota and US Route 12 at Mobridge. The former town of Forest City has been flooded beneath Lake Oahe, about 9 miles west of Gettysburg. Prehistoric archaeological sites have been explored in the area, including Molstad Village near Mobridge. It dates to before the emergence of the Arikara, Hidatsa and Mandan as separate peoples, and has been designated as
Folsom Dam project that provides flood control, hydroelectricity, and irrigation and municipal water supply. In order to increase Sacramento's flood protection to 200 year flood protection (meaning that the area is protected from a flood that has a 0.5% chance of occurring in any given year) the US Army Corps of Engineers is constructing an auxiliary spillway. The spillway was completed by October 2017, and enables Folsom Dam to release water before it reaches the height of the gates already in place. Another Central Valley Project dam, Nimbus Dam, is located further down river. Folsom Dam is located just north of the