Oahe Dam

Six miles north of Pierre the Missouri stops at a ridge of packed earth more than nine thousand feet long. The Army Corps of Engineers began Oahe Dam in 1948 as the largest of the main-stem dams in the Pick-Sloan plan, building it not of concrete but of earth and shale rolled down in layers, and it remains one of the largest rolled-earth dams in the world. Water reaches the powerhouse at its foot through tunnels driven under the embankment, and the plant's turbines send power across the northern plains.

President John F. Kennedy came to dedicate it in August 1962, speaking to a crowd on the face of the dam about water, power and the development of the West. Behind it Lake Oahe filled over the following years until it stretched more than 230 miles upriver, past Mobridge and into North Dakota almost to Bismarck, one of the largest reservoirs in the country. It drew a new economy of walleye fishing, salmon stocking, marinas and lake cabins.

It also drowned the river's timbered bottomland for most of that distance, and the reservoir now covers ground the Standing Rock and Cheyenne River nations had lived on, along with the farms and agency towns that went with it. The Corps' visitor center above the dam tells the engineering story, and a small white mission chapel kept on the bluff nearby is a reminder of the valley under the water.