The Missouri River is the longest river in North america. rising inside the Rocky Mountains of western Montana, the Missouri flows east and south for two,341 miles (three,767 km) before getting into the Mississippi River north of St. Louis, Missouri. The river takes drainage from a in moderation populated, semi-arid watershed of more than 1/2 a million rectangular miles (1,300,000 km2), which includes components of ten U.S. states and Canadian provinces. whilst mixed with the lower Mississippi River, it bureaucracy the arena's fourth longest river device.

For over 12,000 years, people have depended on the Missouri River and its tributaries as a supply of sustenance and transportation. greater than ten most important companies of local individuals populated the watershed, maximum main a nomadic life-style and depending on significant bison herds that after roamed via the incredible Plains. the primary Europeans encountered the river in the late 17th century, and the region exceeded via Spanish and French arms earlier than sooner or later becoming part of the usa via the Louisiana purchase. The Missouri become long believed to be a part of the Northwest Passage – a water route from the Atlantic to the Pacific – but when Lewis and Clark have become the first to travel the river's entire length, they confirmed the mythical pathway to be no greater than a legend.