Mississippi

The Mississippi River, derived from the Ojibwa (Chippewa Indian) language meaning “great river” or literally, “river of the falls,” is the second-longest river in North America, meandering from Lake Itasca in northern Minnesota to the Gulf of Mexico in Louisiana, a journey of over 2,300 miles.

The longest river in North America is its tributary, the Missouri River, with a length of 2,341 miles (3,767 kilometers) from the confluence of the Jefferson River, Madison River and Gallatin River to the Mississippi River. Taken together, the Jefferson, Missouri, and Mississippi form the largest river system in North America with a length of 3,745 miles, making this combination the third-longest river in the world behind the Nile and Amazon rivers. It is the largest river in the Northern Hemisphere. The Mississippi drains all or part of 31 U.S. states and three Canadian provinces and is thus one of the largest watersheds in the world.

One of the most diverse communities of plants and wildlife in the world exist along the Mississippi. It has one of the largest wetlands in the U.S., visited by 40 percent of all the ducks, geese and swans of North America. A habitat for many plants and animals that are not found elsewhere in the world, such as the paddlefish, it is also a roadmap guiding millions of migratory birds and waterfowl to and from their wintering grounds every year. Countless other wildlife use the river and its floodplain as habitat. More than three hundred species of fish are supported by the Mississippi.

Samuel Clemens, otherwise known as Mark Twain, a colorful and well-loved literary figure of 1800's America, centered his books, Life on the Mississippi and Huckleberry Finn from his memories of growing up on “the Mighty Mississippi.”

Geography

Saint Anthony Falls in Minneapolis; the only waterfall along the river's course. The Mississippi passes through several glacial lakes, pine forests, vegetation and cattail marshes before it is joined by tributaries. The retention time from its beginning at Lake Itasca to the end at the Gulf of Mexico is about 90 days.

The Minnesota River and the Illinois River are among the first to join the Mississippi. The Missouri River joins the Mississippi near St. Louis, Missouri. Sometimes referred to as "The Big Muddy," it is the Mississippi's second largest tributary by volume. The Mississippi is also joined by the Ohio River at Cairo, Illinois and the Arkansas River near Arkansas Post, Arkansas. The Atchafalaya River in Louisiana is a major distributary of the Mississippi.

Its triangular drainage area covers about 40 percent of the U.S. and includes all or part of 31 states. It drains most of the area between the Rocky Mountains and the Appalachian Mountains except for the areas drained by Hudson Bay via the Red River of the north, the Great Lakes and the Rio Grande.

The Mississippi forms the borders of eight states: Wisconsin, Iowa, Illinois, Missouri, Kentucky, Arkansas, Tennessee and Mississippi. It runs through two others: Minnesota and Louisiana. The river empties into the Gulf of Mexico about 100 miles (160 kilometers) downstream from New Orleans, Louisiana.

From its source to the Ohio River, the river is called the Upper Mississippi River, from the Ohio to its mouth it is known as the Lower Mississippi. 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, Missouri

• the middle Mississippi, a relatively free-flowing river downstream of the confluence with the Missouri River at St. Louis

A series of 29 locks and dams on the upper Mississippi, most of which were built in the 1930s, is designed primarily to maintain a nine-foot (2.7 meter) deep 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. 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.

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 five thousand years, caused the coastline of south Louisiana to advance toward the Gulf from 15 to 50 miles (25–80 kilometers).

The Mississippi River Delta Basin is defined as all of the land and shallow estuarine area between the two northernmost passes of the Mississippi River and the Gulf of Mexico. The basin is located in Plaquemines Parish, Louisiana, south of the city of Venice.

Course changes

The Illinoian Glacier, about 200,000 to 125,000 years before present, blocked the Mississippi River near present-day Rock Island, Illinois, diverting it to its present channel farther to the west, the current western border of Illinois. The Hennepin Canal roughly follows the ancient channel of the Mississippi downstream from Rock Island to Hennepin. South of Hennepin, Illinois, the current Illinois River is actually following the ancient channel of the Mississippi River (to Alton, Illinois) before the Illinoian glaciation.

Other changes in the course of the river have occurred because of earthquakes along the New Madrid Fault Zone, which lies between the cities of Memphis, Tennessee and St. Louis, Missouri. 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 a failed rift (aulacogen) that formed at the same time as the Gulf of Mexico.

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