What is the longest river in the US – North America?
The longest river in North America formed in response to both Laurentide ice sheet glaciation and to glaciation of the Rocky Mountains.
The Missouri is the longest river in the US – North America. The Missouri flows entirely though the United States, where it crosses seven states: Montana, North Dakota, South Dakota, Nebraska, Iowa, Kansas and Missouri.
The headwaters of the Missouri are located where the Jefferson, Madison and Gallatin rivers meet, in the Rocky Mountains, in Montana, 1,200 metres above sea level. It flows into the Mississippi river as its main tributary, 16 kilometres from the city of St. Louis.
The Missouri is 3,943 kilometres long. If we consider the Mississippi-Missouri river system, the total length would increase to 7,725 kilometres, forming the world’s fourth longest river, after the Amazon, Nile and Yangtze rivers.
The drainage basin spans 1,371,100 square kilometres, making it the sixth largest one in the world, comprising 16,840 square kilometres in southern Canada.
For thousands of years, the Missouri has been home to Native Americans. The first Europeans to discover the river were explorers Jacques Marquette and Louis Jolliet in 1673. After that, explorers Lewis and Clark (1804-1805) were the first to navigate from its headwaters to its mouth.
During the 19th century, steam boat traffic increased until 1858, when it started to decline. In 1944, the US Congress approved a programme for irrigation development, flood control, and hydropower generation.