The Mississippi River

The Mississippi River, 3,779 km (2,348 mi) long, is the second longest river, after the Missouri, in the United States. Its triangular drainage area, covering about 40% of the country and including all or part of 31 states, is approximately 3,250,000 sq km (1,250,000 sq mi), the third largest in the world. The Mississippi rises in Minnesota and then flows south, following the boundaries between the states of Minnesota, Iowa, Missouri, Arkansas, and Louisiana on the west, and Wisconsin, Illinois, Kentucky, Tennessee, and Mississippi on the east. The river, whose name means "father of waters" in the Algonquian language, has long been an important transportation artery of North America.

Course of the River

Rising at an elevation of 446 m (1,463 ft) in Lake Itasca, Minn., the Mississippi flows through several glacial lakes to Minneapolis-Saint Paul, where it passes over a series of rapids and is joined by the Minnesota River. After this confluence, the Mississippi is fringed by 60-90-m-high (200-300-ft) bluffs on both sides.

Between Minneapolis and Saint Louis, Mo., the most important tributaries are the ILLINOIS, Chippewa, Black, Wisconsin, Saint Croix, Iowa, Des Moines, and Rock rivers, some of which drain the nation's most fertile agricultural areas. The MISSOURI RIVER, draining the Great Plains to the west, joins the Mississippi at Saint Louis. It is the longest tributary, and constitutes more than 40% of the Mississippi system drainage area, while furnishing about 20% of the total discharge. At Cairo, Ill., the Mississippi is joined from the east by the OHIO RIVER.

South of Cairo the Mississippi enters a wide (64-113 km/40-70 mi), low valley that was once an embayment of the Gulf of Mexico. Sediment has filled this area, and through the centuries the river has extended its mouth to the present location 966 km (600 mi) downstream. This lower part of the Mississippi's course, characterized by geographers as a typical example of an "old-age" river, is contained within natural levees formed by flood-deposited sediments. Beyond the levees lie low floodplains often at a lower elevation than the river itself. Another feature of the river is its meandering. The channel route from Cairo to New Orleans is almost three times as long as the valley. Major tributaries in the lower section are the ARKANSAS, RED, and White rivers, all flowing from the west.

The Mississippi enters the Gulf of Mexico (see MEXICO, GULF OF) about 160 km (100 mi) downstream from New Orleans, through a 26,150-sq km (10,100-sq mi) delta. Because almost 550 million metric tons (500 million U.S. tons) of sediment are deposited annually, the delta extends about 91 m (300 ft) each year.


Mean annual temperatures range from about 4 deg to 10 deg C (40 deg to 50 deg F) at the Mississippi's source in Minnesota to about 21 deg to 27 deg C (70 deg to 80 deg F) at its mouth. Precipitation along the river's course varies widely, from 510-1,015 mm (20-40 in) in the north to 1,520-1,780 mm (60-70 in) at its New Orleans delta.

Flood Control

In its lower section the Mississippi is subject to disastrous flooding. Efforts at containing the river have been especially vigorous since a catastrophic flood in 1927, when about 67,300 sq km (26,000 sq mi) of land were inundated and the river rose 17 m (57 ft) at Cairo. The federal government has built artificial levees 5-7 m (15-24 ft) high and dredged waterways that release the floodwater laterally to the Gulf of Mexico.

Navigation and Economic Use

The lower river, which has a relatively narrow but deep channel, is navigable for oceangoing ships upstream to Baton Rouge, La. From there to Cairo a 4-m-deep (12-ft) channel is maintained. From Cairo to Minneapolis and on the other navigable streams (the Cumberland, Ohio, Tennessee, Illinois, Arkansas, and Missouri rivers), a 3-m-deep (9-ft) channel is maintained in most places. About 24,150 km (15,000 mi) of the system are presently navigable, and river traffic has experienced significant growth in recent years. The cargoes transported on more than 8,000 towboats consist mainly of petrochemicals from the Gulf of Mexico and grain from the Midwest.

Exploration and Development

The first Europeans to see the river inland were Hernando DE SOTO and his party in 1541. In the late 17th century, the Frenchmen Jacques MARQUETTE and Louis JOLLIET (1673) and the sieur de LA SALLE explored the river from the north; La Salle, who reached the mouth of the Mississippi in 1682, claimed the whole valley for France. The western part of the basin was purchased from France by the United States in 1803 (see LOUISIANA PURCHASE) and was explored by the LEWIS AND CLARK EXPEDITION. Among the original Indian tribes living along the Mississippi were the OJIBWA, WINNEBAGO, FOX, SAUK, CHOCTAW, CHICKASAW, NATCHEZ, and ALABAMA.

The river system formed the pathways for much of the settlement of the central United States. The advent of the steamboat in 1812 brought dependable transportation, and river traffic increased rapidly. During the Civil War control of the river was a major strategic objective; the VICKSBURG CAMPAIGN (1863) achieved that goal for the Union armies. Traffic resumed after the war, and the primacy of the steamboat followed. Eventually the steam paddle-wheelers were replaced by diesel, screw-driven towboats pushing barges. The rivalry between rail and river transport, which started in the late 19th century, persists to this day.

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Bibliography: Burman, Ben L., Look Down That Winding River: An Informal Portrait of the Mississippi (1973); Morris, Wright, ed., The Mississippi River Reader (1962); Twain, Mark, Life on the Mississippi (1883; repr. 1957).

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