Oahe Dam dam upstream is Garrison Dam, near Riverdale, North Dakota, and the next dam downstream is Big Bend Dam, near Fort Thompson, South Dakota. In September and October 1804, the Lewis and Clark Expedition passed through what is now Lake Oahe while exploring the Missouri River. Oahe Dam was authorized by the Flood Control Act of 1944, and construction by the United States Army Corps of Engineers began in 1948. The world’s first rock tunnel boring machine (TBM) was invented in 1952 by James S. Robbins for the Oahe Dam project, which marked the beginning of machines replacing human tunnelers. The
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