Flood control engineering on the Mississippi river is a com posite of all known methods of flood control, which comprise: (a) increasing the flood-carrying capacity of natural river chan nels; (b) construction of levees and flood walls to hold flood wa ter off the land and confine it to established channels; (c) provi sion of floodways or auxiliary channels to carry flows in excess of the capacity of main channel; (d) construction of reservoirs to store flood water temporarily and reduce peak flood flows.
Hernando de Soto, an early Spanish explorer, discovered the lower course of the Mississippi river in 1541. The Spaniards did not follow up his discovery and there is no further record of white men on the river for 132 years. In 1673 two French explorers, Louis Joliet (q.v.) and Father Marquette went from Lake Michigan by the Fox—Wisconsin river route to the Missis sippi and were probably the first white men on the upper course. They voyaged south to the mouth of the Arkansas. In 1682 La Salle (q.v.) entered the Mississippi by the Illinois route and was the first to explore it southward to its mouth. There he took formal possession of the entire drainage basin of the Mississippi for France, naming it "Louisiana" in honour of Louis XIV. Under his orders Michel Accault voyaged northward from the mouth of the Illinois as far as the Falls of St. Anthony in Minnesota, thus completing for France the exploration of the greater part of the river. French settlements were founded at Cahokia and Kaskaskia, Illinois, c. 1700 and New Orleans, 1718.
By the treaty of Paris (1763) that part of the Mississippi valley east of the river (except the site of New Orleans on the east side of the river) was transferred from France to England, while the remainder of the valley was secretly ceded to Spain. The United States by the treaty (1783) at the close of the Revo lutionary War secured title to the British portion. To the settlers already crossing the Alleghenies in great numbers the Ohio and Mississippi rivers furnished the most natural outlet for their prod ucts. Floating these down the river on rafts and flat-boats to New Orleans where they might be transferred to ocean vessels was much cheaper than carrying them overland across the moun tains. To these settlers Spanish control of both sides of the river at New Orleans was a continual annoyance. A treaty with Spain in 1795 secured for Americans the right to deposit goods while they were awaiting transfer to ocean ships, but in 1802 the Spanish Intendant closed the river to all navigation by Americans. In the meantime Spain had transferred Louisiana to France. Indignation in the trans-Allegheny settlements was running so high that President Jefferson authorized Robert Livingston to treat with Napoleon in an effort to purchase enough territory to secure for the United States control of the outlets of the Missis sippi. The unexpected result was the accession of the entire terri tory of Louisiana, comprising the entire western drainage basin of the river.
Early traffic down the Mississippi was mostly by barges or keel-boats, and the return trip was rarely attempted. However,
the chief rush of immigration into the Mississippi valley luckily coincided with the introduction and development of the steam boat. Only four years after Fulton made his memorable journey up the Hudson river, the first steamboat came puffing down the Mississippi. Thirty years later the steamboat period was at its zenith; 3o years more and it had declined before the competition of east—west railways. This was a gay and colourful period in the history of the river, one which furnished later writers with many a theme for romance. It is impossible to overemphasize the con crete contribution made by the steamboat to the development of the Mississippi valley, for waiting for the completion of railways would have postponed its general settlement for a generation. Besides the numerous freight steamers the picturesque, well equipped passenger steamers were a notable feature of the period.
During the Civil War the operations of the western division of the Union army were largely devoted to securing control of the Mississippi. Land operations from the north were supple mented by the brilliant naval operations of Farragut from the South, and finally, with the fall of Vicksburg and Port Hudson, the Confederacy was cut in two and President Lincoln was able to announce that "The Father of the Waters again goes unvexed to the sea." There was some revival of Mississippi commerce after the Civil War, but in addition to the increasing inroads of railways, it was checked by the bar at the mouth of the South west pass. Relief was obtained through the Eads jetties at the mouth of South pass in 1879, but still steamboat companies did not prosper.