Mississippi River

This page is about the river in the United States; there is also a Canadian Mississippi River (Ontario).

Geography

With its source Lake Itasca at 1475 feet (450 m) above sea level in Itasca State Park in northern Minnesota, the river falls to 725 feet (220 m) just below Saint Anthony Falls in Minneapolis. The Mississippi is joined by the Illinois River and the Missouri River near Saint Louis, and by the Ohio at Cairo, Illinois. The Arkansas River joins the Mississippi in the state of Arkansas. The Atchafalaya River in Louisiana is a major distributary of the Mississippi.

Related Topics:
Lake Itasca - Itasca State Park - Minnesota - Saint Anthony Falls - Minneapolis - Illinois River - Missouri River - Saint Louis - Ohio - Cairo, Illinois - Arkansas River - Arkansas - Atchafalaya River - Louisiana - Distributary

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The Mississippi drains most of the area between the Rocky Mountains and the Appalachian Mountains, except for the area drained by the Great Lakes. It runs through, or borders, ten states in the United States -- Minnesota, Wisconsin, Iowa, Illinois, Missouri, Kentucky, Arkansas, Tennessee, Mississippi and Louisiana -- before emptying into the Gulf of Mexico about 100 miles (160 km) downstream from New Orleans. Measurements of the length of the Mississippi from Lake Itasca to the Gulf of Mexico vary, but the EPA's number is 2,320 miles (3733 km). A raindrop falling in Lake Itasca would arrive at the Gulf of Mexico in about 90 days. http://www.nps.gov/miss/features/factoids/

Related Topics:
Rocky Mountains - Appalachian Mountains - Great Lakes - United States - Minnesota - Wisconsin - Iowa - Illinois - Missouri - Kentucky - Arkansas - Tennessee - Mississippi - Louisiana - Gulf of Mexico - New Orleans

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The river is divided into the upper Mississippi, from its source south to the Ohio River, and the lower Mississippi, from the Ohio to its mouth near New Orleans. The upper Mississippi is further divided into three sections: the headwaters, from the source to Saint Anthony Falls; a series of man-made lakes between Minneapolis and St. Louis; and the middle Mississippi, a relatively free-flowing river downstream of the confluence with the Missouri River at St. Louis.

Related Topics:
Ohio River - New Orleans - Saint Anthony Falls - St. Louis - Missouri River

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A series of 27 locks and dams on the upper Mississippi, most of which were built in the 1930s, is designed primarily to maintain a 9 foot (2.7 m) channel for commercial barge traffic. The lakes formed are also used for recreational boating and fishing. The dams make the river deeper and wider but do not stop it. No flood control is intended. During periods of high flow, the gates, some of which are submersible, are completely opened and the dams simply cease to function. Below St. Louis the Mississippi is relatively free-flowing, although it is constrained by numerous levees and directed by numerous wing dams.

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Through a natural process known as deltaic switching the lower Mississippi River has shifted its final course to the ocean every thousand years or so. This occurs because the deposits of silt and sediment raise the river's level causing it to eventually find a steeper route to the Gulf of Mexico. The abandoned distributary diminishes in volume and forms what are known as bayous. This process has, over the past 5,000 years, caused the coastline of south Louisiana to advance gulfward from 15 to 50 miles.

Related Topics:
Deltaic switching - Gulf of Mexico - Bayou

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(See: Mississippi River Delta)

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Other changes in the course of the river have occurred because of earthquakes along the New Madrid Fault Zone, which lies near the cities of Memphis and St. Louis. Three earthquakes in 1811 and 1812, estimated at approximately 8 on the Richter Scale, were said to have temporarily reversed the course of the Mississippi. These earthquakes also created Reelfoot Lake in Tennessee from the altered landscape near the river. The faulting is related to an aulacogen (geologic term for a failed rift) that formed at the same time as the Gulf of Mexico.

Related Topics:
New Madrid Fault Zone - Memphis - St. Louis - Earthquake - Richter Scale - Reelfoot Lake - Aulacogen - Gulf of Mexico

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Davenport, Iowa is the only city over 20,000 people bordering the Upper Mississippi that has no permanent floodwall or levee.

Related Topics:
Davenport, Iowa - Floodwall - Levee

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Watershed

The Mississippi River has the third largest drainage basin in the world, exceeded in size only by the watersheds of the Amazon River and Congo River. It drains 41 percent of the 48 contiguous states of the United States. The basin covers more than 1,245,000 square miles (3,225,000 km²), including all or parts of 31 states and two Canadian provinces.

Related Topics:
Amazon River - Congo River - Contiguous states of the United States - 3,225,000 km²

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• Information and a map of the Mississippi's watershed