MISSOURI RIVER, in the central and northwest central United States, is a major tributary of the Mississippi River and the longest river in the United States (2,466 miles). It drains a watershed of approximately 580,000 square miles. Father Jacques Marquette and Louis Jolliet reached the mouth of the Missouri in 1673. It was known to them as Peki-tan-oui, so named on some of the early maps, and later as Oumessourit. From its source in southwestern Montana, where the Jefferson, Gallatin, and Madison Rivers join together, it winds around hills and bluffs, through one of the most fertile valleys in the world, to its junction with the Mississippi (ten miles north of Saint Louis).
The lower part of the Missouri was known to the French trappers, traders, and voyageurs, who ascended it as far as the Kansas River in 1705. In 1720 a Spanish caravan was sent from Santa Fe to the Missouri to drive back the French. The early French called the river Saint Philip. They probably did not go higher than the Platte, which was considered the dividing line between the upper and lower river. In 1719 Claude Charles du Tisne and party went up the Missouri in canoes as far as the Grand River. Credited with being the first white man to visit the upper Missouri country, Pierre Gaultier de Varennes, Sieur de La Vérendrye, led a party from one of the posts of the Hudson's Bay Company in 1738 to the Mandan villages. Other explorations followed, searching for the "Western Sea" by way of the Missouri River. The Missouri was first explored from its mouth to its source by Meriwether Lewis and William Clark (1804–1805).
Although it was thought for years that no keelboat could ascend the Missouri, it later became the great highway into the West. Gregoire Sarpy is said to have first introduced the keelboat, but the real father of navigation on the Missouri was Manuel Lisa. The first steamboat ever to ascend the river was the Independence, which pushed off from Saint Louis in 1819, reached Old Franklin in thirteen days, and turned back at Old Chariton, in Missouri. In 1831, Pierre Chouteau succeeded in ascending the Missouri in his steamboat Yellowstone. As a result of steamboating, many cities grew up along the edge of the river and several states built their capitals on its bank. Steamboating on the river reached its peak in the late 1850s and declined following the completion in 1859 of the Hannibal and Saint Joseph Railroad.
The Missouri River has always carried in suspension an immense amount of solid matter, mostly very fine light sand, discoloring the water and justifying the name of "Big Muddy." It is said that the yearly average of solid matter carried into the Mississippi by this river is over 500 million tons, brought along for an average distance of 500 miles. While the Missouri has a greater annual flow of water than the Mississippi above its mouth, it is subject to greater fluctuations. These have affected its navigability in certain seasons and caused the shoreline to shift, some farms and villages to disappear, and others to be left far back through deposits of the soil in front of them.
In 1944 Congress authorized a Missouri River basin project to control flooding of the Missouri, improve navigation, develop hydroelectric power, irrigate more than 4.3 million acres in the basin, halt stream pollution, and provide recreation areas. By the 1970s there were seven dams on the Missouri and eighty on its tributaries. The Missouri Basin Interagency Committee, with representatives from seven federal agencies and the governors of the ten Missouri basin states (North Dakota, South Dakota, Wyoming, Nebraska, Kansas, Minnesota, Missouri, Colorado, Iowa, and Montana), oversees the project. In the late twentieth century, the urbanization, soil erosion, and pollution had made the Missouri River one of the nation's most endangered rivers.
Brower, Jacob V. The Missouri River and Its Utmost Source; Curtailed Narration of Geologic, Primitive and Geographic Distinctions Descriptive of the Evolution and Discovery of the River and Its Headwaters. St. Paul, Minn.: Pioneer Press, 1896, 1897.
DeVoto, Bernard A. Across the Wide Missouri: 1897–1955. Boston: Houghton Mifflin, 1947, 1987; New York: American Legacy Press, 1981.
Griffith, Cecil R. The Missouri River: The River Rat's Guide to Missouri River History and Folklore. Leawood, Kans.: Squire Publishers, 1974.
Stella M.Drumm/a. g.
The Missouri River is the longest river in the United States. It flows for 2,466 miles (3,968 kilometers). Its source lies in the Rocky Mountains of southwestern Montana; the river is formed by the confluence of the Jefferson, Madison, and Gallatin rivers at Three Forks, Montana. From there the Missouri flows east and southeast, ultimately joining the Mississippi River about 10 miles (16 kilometers) north of St. Louis, Missouri. The Missouri River flows through Montana, North Dakota, South Dakota, Nebraska, Iowa, Kansas, and Missouri. From the Mississippi River, the Missouri is navigable by barges and towboats west and north as far as Sioux City, Iowa. Above Sioux City the water flow is controlled by a series of dams in a project authorized by the U.S. government in 1944. When the water is high the river is navigable to Great Falls (northeast of Helena), Montana.
In 1673 the mouth of the Missouri was passed by French-Canadian adventurer Louis Jolliet (1645–1700) and French missionary Jacques Marquette (1637–75) as they explored the upper part of the Mississippi River. The Lewis and Clark expedition of 1804–06 followed the Missouri for much of the journey to the Pacific Ocean.
During the first two decades of the 1800s, the river provided a chief transportation route for the western fur trade, which relied on keel boats to move goods along the river. In 1819 steamboat traffic began on the waterway, carrying pioneers to the rugged West. Riverboat traffic declined with the expansion of the cross-continental railroads at the end of the nineteenth century. Much of the region through which the Missouri River flows—the interior plains—was the last frontier to be settled in America.
See also: Fur Trade, Louisiana Purchase, Lewis and Clark Expedition, Mississippi River, Steamboats