Mississippi River

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The Spanish explorer Hernando De Soto is credited with the European discovery of the Mississippi River in 1541. The French explorers Jacques Marquette and Louis Jolliet reached it through the Wisconsin River in 1673, while La Salle traveled down the river to the Gulf of Mexico in 1682 and claimed the entire territory for France. The French founded New Orleans in 1718 and effectively extended control over the upper river basin with settlements at Cahokia, Kaskaskia, Prairie du Chien and Saint Louis. France ceded the river to Spain in 1763 but regained it in 1800. The United States acquired the Mississippi River as part of the Louisiana Purchase in 1803.

The Mississippi was originally a major artery for the Native Americans and later very important for fur-trading French. In the 19th century, the river became the principal outlet for the newly settled areas of mid-America. Exports were floated downstream with the current, while imports were poled or dragged upstream on rafts and keelboats. The first steamboat plied the river in 1811 and successors became more and more luxurious as river trade increased in profitability and importance. That era is colorfully described in Mark Twain's 1883 book Life on the Mississippi.

River traffic from the north ceased after the outbreak of the Civil War. During that war, the Mississippi was an invasion route for Union armies and the scene of many battles. Especially decisive were the capture of New Orleans in 1862 by Admiral David Farragut, who was the Union naval commander and the victory of Union forces under Grant at Vicksburg in 1863. River traffic resumed after the war, but much of the trade was lost to the railroads. Later, modern improvements in the channels of the river has increased traffic again, especially since the mid-1950's, with principal freight items being petroleum products, chemicals, sand, gravel and limestone.

The Mississippi is the second-longest river in the United States and exceeded in length only by the Missouri River, the chief of its numerous tributaries. The combined Missouri-Mississippi system, measured from the Missouri's headwaters in the Rocky Mountains, to the mouth of the Mississippi River, is 6,020 km (3,740 miles) long and ranks as the world's third longest river system after the Nile and the Amazon. The Mississippi itself is 3,780 km (2,350 miles) long. With its tributaries, the Mississippi drains 3,188,290 km² (1,231,000 sq miles) of the central United States, including all or part of 31 states and some 33,670 km² (13,000 sq miles) of Alberta and Saskatchewan in Canada. Cotton and rice are important crops in the lower Mississippi valley, while sugarcane is raised in the delta. The Mississippi is abundant in freshwater fish and shrimp are taken from the briny delta waters. The delta also yields sulfur, oil and gas.

The Mississippi River rises in small streams that feed Lake Itasca, at an altitude of 446 m (1,463 feet) in northern Minnesota and flows generally south to enter the Gulf of Mexico through a huge delta in southeastern Louisiana. The Mississippi River is a major economic waterway and navigable from the sediment-free channel maintained through South Pass in the delta to the Falls of Saint Anthony in Minneapolis. Canals circumvent the rapids near Rock Island, Illinois and Keokuk, Iowa. For the low-water months of July, August and September, there is a 13.7 m (45 feet) wide channel navigable by oceangoing vessels from Head of the Passes to Baton Rouge, Louisiana and a 2.7 m (9 feet) wide channel from Baton Rouge to Minneapolis, which is deep enough for barges and towboats. The Mississippi connects with the Intracoastal Waterway in the south and with the Great Lakes-Saint Lawrence Seaway system in the north by way of the Illinois Waterway.

Along the river's upper course, shipping is usually interrupted by ice from December to March. Thick, hazardous fogs frequently settle on the cold waters of the unfrozen sections during warm spells from December to May. In its upper course the river is controlled by numerous dams and falls to overcome the 210 m (700 feet) of altitude difference in the 826 km (513 miles) stretch from Lake Itasca to Minneapolis. After that, the Mississippi falls a further 150 m (490 feet) in the 1,378 km (856 miles) stretch from Minneapolis to Cairo, Illinois. The Mississippi receives the Missouri River 27 km (17 miles) north of Saint Louis and expands to a width of 1,070 m (3,500 feet). At Cairo, it becomes even wider and swells to 1,370 m (4,500 feet) after receiving the Ohio River.

The lower Mississippi meanders in great loops across a broad alluvial plain, which is between 40 and 201 km (25-125 miles) wide. The plain stretches from Cape Girardeau, Missouri, to the delta region south of Natchez, Mississippi. It is marked with oxbow lakes and marshes that are remnants of the river's former channels. Natural levees, built up from sediment carried and deposited in times of flood, border the river for much of its length. Sediment has also been deposited on the riverbed, so, in places the surface of the Mississippi is above that of the surrounding plain, as evidenced by the river basins of the Saint Francis, Black, Yazoo and Tensas rivers. Breaks in the levees frequently flood the fertile bottomlands of these and other low-lying areas of the plain.

Mississippi Delta

After receiving the Arkansas and Red rivers, the Mississippi forms a large delta, which was built outward by sediment carried by the main stream since 1500 A.D. It then discharges into the Gulf of Mexico through a number of distributaries, the most important being the Atchafalaya River and Bayou Lafourche. The main stream continues southeast through the delta to enter the gulf through several mouths, including Southeast Pass, South Pass and Pass à Loutre. Indications that the Mississippi River might abandon this course and divert through the Atchafalaya River led to the construction of a series of dams, locks and canals by the U.S. Army Corps of Engineers. The effort is known as the Old River Control Structure and was undertaken to prevent such an occurrence. Sluggish bayous and freshwater lakes, such as Pontchartrain, Grand and Salvador, dot the delta region.

Regarding the delta, environmentalists and those in the seafood industry are concerned by the loss of 65 to 104 km² (25-45 sq miles) of marsh every year. Fish and wildlife populations are threatened, because their natural habitat slowly disappears. The loss has been attributed to subsidence and a decrease in sediment largely due to dams, artificial channeling and land conservation measures. Pollution and the cutting of new waterways for petroleum exploration and drilling have also taken their toll on the delta. Louisiana has enacted environmental protection laws that are expected to slow, but not halt, the loss of the delta marshes.

Flood Control

The flow of the Mississippi River is greatest in the spring, when heavy rainfall and melting snow on the tributaries, especially the Missouri and the Ohio, cause the main stream to rise and frequently overflow its banks and levees, inundating vast areas of the plain. Since the disastrous flood of 1927, the U.S. Congress has authorized the construction of dams on the upper Mississippi and its tributaries to regulate the flow. The plans also included the building of 2,580 km (1,600 miles) of levees below Cape Girardeau to contain the swollen river and the establishment of floodways to divert water at critical points, such as the Cairo-New Madrid, Atchafalaya and Morganza floodways and the Bonnet Carre Spillway at New Orleans, which diverts water into Lake Pontchartrain. Cutoffs have eliminated the dangerous winding channels and an improved main channel has increased the river's flood-carrying capacity. At Clinton, Mississippi, you can see an 89 hectares (220 acres) large model of the Mississippi River basin. It was formerly used by the U.S. Corps of Engineers to simulate various conditions in the basin.

Nonetheless, serious, record-breaking floods again occurred in the rainy spring of 1973, when the river crested at Saint Louis at 13.2 m (43.3 feet) and again in the summer of 1993, when the river crested at Saint Louis at 15.1 m (49.6 feet), killing 50 people, displacing 50,000 and causing $12 billion in agricultural and property damage. The narrow river channel that has been created by building levees has worsened flooding in some instances. In 1988 a severe drought brought water levels down to their lowest point in recorded history and halted most river traffic.