Garrison Dam, c.11,300 ft (3,400 m) long and 210 ft (64 m) high, on the Missouri River, near Riverdale, W central N.Dak.; one of the world's largest earth-filled dams used for irrigation power. Built by the U.S. Army Corps of Engineers (completed 1956), it is a key unit in the Missouri River basin project. It impounds Lake Sakakawea.
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