The Missouri River got its name from a Sioux Indian tribe called the Missouris. This tribe gave both the state and the river their names. According to the Smithsonian Institution Bureau of American Ethnology, "Missouri" is translated as "town of the large canoes."
Other authorities have stated the translation is "he of the big canoe" or "wooden canoe people." The Missouri River flows down from the Rocky Mountains in Montana for 2,341 miles and then enters the Mississippi River north of St. Louis. It is the longest river in the United States, and in fact in all of North America.