The Mississippi River Alluvial Plain is an alluvial plain created by the Mississippi River on which lie parts of seven U.S. states, from southern Louisiana to southern Illinois (Illinois, Missouri, Kentucky, Tennessee, Arkansas, Mississippi, Louisiana).
The plain is divided into (a) the Mississippi River Delta in the southern half of Louisiana and (b) the upper Mississippi Embayment running from central Louisiana to Illinois.
The Arkansas Post (French: Poste de Arkansea; Spanish: Puesto de Arkansas), officially the Arkansas Post National Memorial, was the first European settlement located along the Mississippi River, in the Mississippi Alluvial Plain, and in the present-day U.S. state of Arkansas. In 1686, Henri de Tonti established it on behalf of Louis XIV of France for the purpose of trading with the Quapaw Nation.
The French, Spanish, and Americans, who acquired the territory in 1803 with the Louisiana Purchase, considered the site of strategic value. It was the capital of Arkansas from 1819 until 1821 when the territorial government relocated to Little Rock.
The Mississippi embayment is a physiographic feature in the south-central United States, part of the Mississippi Alluvial Plain. It is essentially a northward continuation of the fluvial sediments of the Mississippi River Delta to its confluence with the Ohio River at Cairo, Illinois. The current sedimentary area was formed in the Cretaceous and early Cenozoic by the filling with sediment of a pre-existing basin. An explanation for the embayment's formation was put forward by Van Arsdale and Cox in 2007: movement of the Earth's crust brought this region over a volcanic "hotspot" in the Earth's mantle causing an upthrust of magma which formed the Appalachian-Ouachita range. Subsequent erosion caused a deep trough that was flooded by the Gulf of Mexico and eventually filled with sediment from the Mississippi River.
The Arkansas Delta is one of the six natural regions of the state of Arkansas. Willard B. Gatewood Jr., author of The Arkansas Delta: Land of Paradox, says that rich cotton lands of the Arkansas Delta make that area "The Deepest of the Deep South."
The region runs along the Mississippi River from Eudora north to Blytheville and as far west as Little Rock. It is part of the Mississippi embayment, itself part of the Mississippi River Alluvial Plain. The flat plain is bisected by Crowley's Ridge, a narrow band of rolling hills rising 250 to 500 feet (76 to 152 m) above the flat delta plains. Several towns and cities have been developed along Crowley's Ridge, including Jonesboro. The region's lower western border follows the Arkansas River just outside Little Rock down through Pine Bluff. There the border shifts to Bayou Bartholomew, stretching south to the Arkansas-Louisiana state line.