Question: How long is the river that contains Colter Falls?

The Missouri River is the longest river in North America.  Rising in the Rocky Mountains of western Montana, the Missouri flows east and south for 2341 mi before entering the Mississippi River north of St. Louis, Missouri.  The river takes drainage from a sparsely populated, semi-arid watershed of more than half a million square miles (1,300,000 km), which includes parts of ten U.S. states and two Canadian provinces.  When combined with the lower Mississippi River, it forms the world's fourth longest river system. <SEP> Black Eagle Dam is a hydroelectric gravity weir dam located on the Missouri River in the city of Great Falls, Montana.  The first dam on the site, built and opened in 1890, was a timber-and-rock crib dam.  This structure was the first hydroelectric dam built in Montana and the first built on the Missouri River.  The dam helped give the city of Great Falls the nickname "The Electric City."  A second dam, built of concrete in 1926 and opened in 1927, replaced the first dam, which was not removed and lies submerged in the reservoir.  Almost unchanged since 1926, the dam is 782 ft long and 34.5 ft high, and its powerhouse contains three turbines capable of generating seven megawatts (MW) of power each.  The maximum power output of the dam is 18 MW.  Montana Power Company built the second dam, PPL Corporation purchased it in 1997 and sold it to NorthWestern Corporation in 2014.  The reservoir behind the dam has no official name, but was called the Long Pool for many years.  The reservoir is about 2 mi long, and has a storage capacity of 1,710 acre.ft to 1,820 acre.ft of water. <SEP>  Downstream of Colter Falls lies Rainbow Falls, and upstream is Black Eagle Falls.  The Lewis and Clark Expedition was known to discover Westslope cutthroat trout at the base of the falls.  The falls is now flooded in the impoundment behind Rainbow Dam.  As Rainbow Dam's reservoir is a run-of-the-river reservoir, it rarely is emptied, so the falls is rarely seen even in extreme drought.  The falls was named by Paris Gibson, founder of the city of Great Falls, Montana, while they were not named by Lewis and Clark, who measured it at "6 feet 7 inches". Colter Falls, also Coulter Falls, (4.3m) waterfall, nearly 0.5 mi in width, part of the Great Falls of the Missouri, on the Missouri River in north-central Montana. <SEP> Rainbow Falls (originally "Handsome Falls") is a waterfall on the Missouri River in Great Falls, Montana, just upstream from Crooked Falls and downstream from Colter Falls and Rainbow Dam.  It is 47 feet (14m) high and 1,320 feet (402.3m) wide.  The waterfall is part of the five Great Falls of the Missouri.  The river spills over a sheer ledge of sandstone in the Kootenai Formation, forming the falls.  The falls used to flow with a great deal of force year-round.  In 1914 the river shortly upstream was dammed for hydroelectric power by the Rainbow Dam, which forms a run-of-the-river reservoir.  As a result, the falls can almost totally dry up in the summer with only a few narrow strips of water trickling down its face.  A railroad bridge crosses the river directly above the falls.