High Quality Content by WIKIPEDIA articles! 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 and just upstream of Rainbow Falls, a 45 ft (14m) waterfall that is the third of the five Great Falls of the Missouri. The dam, built in 1910, generates 36 MW of electricity from 8 turbines. Building the dam reduced the flow of water over Rainbow Falls and downstream Crooked Falls, and they can almost completely dry up if less water exits the dam. The water from the penstocks re-enters the river a few hundred yards east of Crooked Falls.