Oahe was created between 1948 and 1962, and is one of six major impoundments along the upper Missouri River. The lake has 2,250 miles of basically undeveloped shoreline. Overall, Oahe can be described as rocky and sandy with moderate to clear water. There is extremely deep water close to the shoreline in many areas, but most of the canyons become shallow enough for excellent topwater, jig, and crankbait fishing. On the lower end, the only vegetation to be found is scattered shoreline grass in the very backs of the canyons.
Forage is abundant and includes the spottail shiner, goldeneye, perch, and emerald shiner.
The upper part of the lake is essentially a river-type environment, although with a number of backwater sloughs that are filled with standing timber, brush, reeds, and other vegetation. This is where the largemouth are caught. These shallow backwaters are out of the current and somewhat reminiscent of what bass fishermen find on some southern waterways. Spinnerbaits and even buzzbaits can be used here throughout the spring and summer. At the city of Mobridge, South Dakota, the lake gradually begins to widen although still retaining the overall appearance of a huge river.