Missouri( Missouri River, derived from the Missouri tribe and meaning "people with wooden canoes") is the longest river in North America. It flows through the northern United States in a southeasterly direction through seven states - Montana, North Dakota, South Dakota, Nebraska, Iowa, Kansas and Missouri - until it empties into the Mississippi River, of which it is its main tributary, very close to the city of St. Louis. It has a length of 4090 km, but if the Mississippi-Missouri system is considered, it reaches 6275 km, which places it as the fourth longest in the world, after the Amazon, Nile and Yangtze rivers.