Garrison Dam is an earth-fill embankment dam on the Missouri River in central North Dakota, U.S. Constructed by the U.S. Army Corps of Engineers from 1947 to 1953, at over two miles (3.2 km) in length, the dam is the fifth-largest earthen dam in the world. The reservoir impounded by the dam is Lake Sakakawea, which extends to Williston and the confluence with the Yellowstone River, near the Montana border. The dam and resulting reservoir inundated approximately one-sixth (16.6%) to one-fourth (25%) of Fort Berthold Indian Reservation's land, resulting in the loss of homes, farmland, and community infrastructure for the Three Affiliated Tribes.