The Missouri is the longest river in the United States, flowing more than 2,500 miles from its source on the eastern slope of the Rockies near Three Forks, Montana, to its confluence with the Mississippi River at St. Louis, Missouri. Congress designated 149 miles of the Upper Missouri (UMNWSR) as a component of the National Wild and Scenic River System in 1976, calling it an irreplaceable legacy of the historic American west. Congress further stated that the river, with its immediate environments, possesses outstanding scenic, recreational, geological, fish and wildlife, historic, cultural, and other similar values. BLM was directed to preserve the Upper Missouri River in a free-flowing condition and protect it for the benefit of present and future generations.
The UMNWSR boundary starts at Fort Benton, Montana, and runs 149 miles downstream ending at the James Kipp Recreation Area.