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
Norris Dam State Park the Norris Project in the 1930s, is located a few miles south of the dam. Norris Dam State Park is located entirely within the Appalachian Ridge-and-Valley Range, which is characterized by narrow elongated ridges flanked by broad, fertile river valleys. The low rolling hills that dominate the park's terrain are underlain by sedimentary rocks— namely limestone, dolomite, shale, and sandstone— which were formed roughly 400-500 million years ago during the Paleozoic Era. Most of Norris Dam State Park is coated by an Appalachian oak-pine forest, much of which is second-growth, although significant old growth stands remain in nearby Chuck Swan