The Mississippi River Alluvial Plain is an alluvial plain created by the

Mississippi River The Mississippi River is the main stem, primary river of the largest drainage basin in the United States. It is the second-longest river in the United States, behind only the Missouri River, Missouri. From its traditional source of Lake Ita ...

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 Louisiana ( ; ; ) is a state in the Deep South and South Central regions of the United States. It borders Texas to the west, Arkansas to the north, and Mississippi to the east. Of the 50 U.S. states, it ranks 31st in area and 25 ...

and (b) the upper Mississippi Embayment running from central Louisiana to Illinois. The term "Mississippi embayment" is sometimes used more narrowly to refer to its section on the western side of the river, running through eastern

Arkansas Arkansas ( ) is a landlocked state in the West South Central region of the Southern United States. It borders Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, Texas to the southwest, and Oklahoma ...

, southeastern Missouri, westernmost

Tennessee Tennessee (, ), officially the State of Tennessee, is a landlocked U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders Kentucky to the north, Virginia to the northeast, North Carolina t ...

(east side of the River), westernmost

Kentucky Kentucky (, ), officially the Commonwealth of Kentucky, is a landlocked U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders Illinois, Indiana, and Ohio to the north, West Virginia to the ...

(east side of the River) and southernmost

Illinois Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern United States. It borders on Lake Michigan to its northeast, the Mississippi River to its west, and the Wabash River, Wabash and Ohio River, Ohio rivers to its ...

, and excluding northwest

Mississippi Mississippi ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South regions of the United States. It borders Tennessee to the north, Alabama to the east, the Gulf of Mexico to the south, Louisiana to the s ...

where the alluvial plain is known as the Mississippi Delta. Most of the alluvium in the lower Mississippi valley is thought to be sourced from the west.Steponaitis, Vincas P., et al. “Large-Scale Patterns in the Chemical Composition of Mississippian Pottery.” ''American Antiquity'', vol. 61, no. 3, 1996, p. 562
JSTOR website
Retrieved 29 May 2025. It is the largest

ecoregion An ecoregion (ecological region) is an ecological and geographic area that exists on multiple different levels, defined by type, quality, and quantity of environmental resources. Ecoregions cover relatively large areas of land or water, and c ...

, covering , and including all of the historic Mississippi River

floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high Discharge (hydrolog ...

in the state.

References

Mississippi River Mississippi embayment Floodplains of the United States Plains of the United States Physiographic sections {{Louisiana-geo-stub