Some 66.5 million cubic yards of dirt compose Garrison Dam , one of the world's largest earth-filled dams. It is 2.5 miles long and 210 feet high, tapering from a half-mile wide at the base to 60 feet at the summit. The dam, which controls the floodwaters of the Missouri River Basin, impounds Lake Sakakawea. The powerhouse produces some 2 million megawatts of electricity annually. Access is via SR 200, which crosses the crest of the dam. Free guided tours are offered; phone (701) 654-7411 for the tour schedule. Learn More...