Neptune's Needle

Principal river of the U.S. c.2,350 miles long, exceeded in length only by the Missouri R., chief of its numerous tributaries. The combined Missouri-Mississippi system (from the Missouri's headwaters in the Rocky Mts. to the mouth of the Mississippi R.) is c.3,740 miles long and ranks as the world's 3d-longest river system after the Nile and the Amazon. With its tributaries, the Mississippi drains c.1,231,000 sq miles of the central United States, including all or part of 31 states and c.13,000 sq miles of Alberta and Saskatchewan in Canada. The Mississippi R. rises in small streams that feed L. Itasca (alt. 1,463 ft/446 m) in N Minnesota; flows generally S to enter the Gulf of Mexico through a huge delta in SE Louisiana. A major economic waterway, the river is navigable from the sediment-free channel maintained through South Pass in the delta to the Falls of St. Anthony in Minneapolis, with canals circumventing the rapids near Rock Island, Ill., and Keokuk, Iowa. For the low-water months of July, August, and September, there is a 45-ft/13.7-m channel navigable by oceangoing vessels from Head of the Passes to Baton Rouge, La., and a 9-ft/2.7-m channel from Baton Rouge deep enough for barges and towboats to Minneapolis. The Mississippi connects with the Intracoastal Waterway in the S and with the Great Lakes-St. Lawrence Seaway system in the N by way of the Illinois Waterway. Along the river's upper course shipping is interrupted by ice from Dec. to March; thick, hazardous fogs frequently settle on the cold waters of the unfrozen sections during warm spells from Dec. to May. In its upper course the river is controlled by numerous dams and falls (c.700 ft) in the 513-mile stretch from L. Itasca to Minneapolis and then falls (c.490 ft) in 856 miles from Minneapolis to Cairo, Ill. The Mississippi R. receives the Missouri R. 17 miles N of St. Louis and expands to a width of c.3,500 ft; it swells to c.4,500 ft at Cairo, where it receives the Ohio R. The lower Mississippi meanders in great loops across a broad alluvial plain (25-125 miles wide) that stretches from Cape Girardeau, Mo., to the delta region S of Natchez, Miss. The plain 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 river bed, so that in places the surface of the Mississippi is above that of the surrounding plain, as evidenced by the St. Francis, Black, Yazoo, and Tensas river basins. Breaks in the levees frequently flood the fertile bottomlands of these and other low-lying areas of the plain. After receiving the Arkansas and Red rivers, the Mississippi enters a birdsfoot-type delta, which was built outward by sediment carried by the main stream since A.D. c.1500. It then discharges into the Gulf of Mexico through a number of distributaries, the most important being the Atchafalaya R. and Bayou Lafourche. The main stream continues SE through the Delta to enter the Gulf through several mouths, including Southeast Pass, South Pass, and Pass � Loutre. Indications that the Mississippi R. might abandon this course and divert through the Atchafalaya R. have led to the construction of a dam by the U.S. Army Corps of Engineers, known as the Old River Control Structure, to prevent such an occurrence. Regarding the Delta, environmentalists and those in the seafood industry are concerned with the fact that it loses 25 sq mi/65 sq km-45 sq mi/117 sq km of marsh a year. 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. Sluggish bayous and freshwater lakes dot the Delta region. The flow of the 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 building of c.1,600 mi/2,580 km 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 L. Pontchartrain. Cutoffs have eliminated the dangerous winding channels, and an improved main channel has increased the river's flood-carrying capacity. Nonetheless, serious, record-breaking floods again occurred in the rainy spring of 1973, when the river crested at St. Louis at 43.3 ft/13.2 m, remained at flood stage for 77 days, and drove about 50,000 persons from their homes and again in 1993. In 1988 a severe drought brought water levels down to their lowest point in recorded history and halted most river traffic. The Span. explorer Hernando De Soto is credited with the Eur. discovery of the Mississippi R. in 1541. The French explorers Jacques Marquette and Louis Joliet reached it through the Wisconsin R. in 1673, and in 1682, La Salle traveled down the river to the Gulf of Mexico 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 St. Louis. France ceded the river to Spain in 1763 but regained it in 1800; the United States acquired the Mississippi R. as part of the Louisiana Purchase in 1803. A major artery for Native Americans and the fur-trading Fr., the river became in the 19th cent. the principal outlet for the newly settled areas of mid-America; exports were floated downstream with the current, and imports were poled or dragged upstream on rafts and keelboats. The 1st steamboat plied the river in 1811, and successors became increasingly luxurious as river trade increased in profitability and importance. Traffic from the north ceased after the outbreak of the Civil War. During the Civil War the Mississippi was an invasion route for Union armies and the scene of many important battles. Especially decisive were the capture of New Orleans (1862) by Adm. David Farragut, the Union naval commander, and the victory of Union forces under General Grant at Vicksburg in 1863. River traffic resumed after the end of the war; it is colorfully described in Mark Twain's Life on the Mississippi (1883). However, much of the trade was lost to the RR in the mid-1800s. With modern improvements in the river channels, traffic has increased, especially since the mid-1950s, with principal freight items being petroleum products, chemicals, sand, gravel, and limestone. Cotton and rice are important crops in the lower Mississippi valley; sugarcane is raised in the Delta. The Mississippi is abundant in freshwater fish; shrimp are taken from the briny Delta waters. The Delta also yields sulfur, oil, and gas.

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Compiler

Peter Richards