Construction of the Oahe Dam on the Missouri River northwest of Pierre began in 1948.* It took ten years and more than 93 million cubic yards of dirt, rock, and concrete to build the dam and the various structures around it. Final closure was accomplished on August 3, 1958.
The film clip below shows workers using heavy machinery to move earth and rock. The film also shows a portion of the 1958 closure, which was accomplished in one relatively rapid, continuous effort over the course of just hours.
It took almost four years for the water level in Lake Oahe to reach it's "minimum operating pool," a volume of water large enough to allow power generation. President John F. Kennedy dedicated the dam on August 17, 1962, the date on which the power station went online. (See film and photos of Kennedy and listen to an audio clip of his speech at the dam in this entry.)
When it was built, Oahe Dam was the second largest rolled-earth dam in the world. It's reservoir created the 4th largest reservoir in the United States.
Learn more about Oahe and the other dams on the Missouri River in this SDPB documentary, which focuses on the record-breaking Missouri River floods of 2011.
For Teachers: Activity idea is available at SDPB's Digital Learning Library.
Source: U.S. Army Corps of Engineers