Rainbow Dam is a hydroelectric dam on the Missouri River, 29 feet (8.8 m) high and 1,055 feet (322 m) long, located six miles northeast of Great Falls in the U.S. state of Montana. The dam is named for the downstream Rainbow Falls, a 45 ft (14 m) waterfall that is the third of the five Great Falls of the Missouri. Built in 1910, the dam furnishes water to an eight-unit hydroelectric plant with a capacity of 36 megawatts. As the dam's power plant is located over a half-mile downstream, the flow of water over Rainbow Falls and downstream Crooked Falls is significantly reduced during the dry season.