Plains (United States)

Plains (United States)
Name	Plains (United States)
Country	United States
States	Kansas; Nebraska; South Dakota; North Dakota; Oklahoma; Texas; Colorado; Wyoming; Montana; New Mexico; Iowa; Minnesota; Missouri

Contents

Plains (United States) is a broad physiographic region of the central United States characterized by extensive flatlands, rolling hills, and grassland ecosystems stretching between the Mississippi River, the Rocky Mountains, and the Canadian Prairies. The region has played central roles in episodes such as the Lewis and Clark Expedition, the Louisiana Purchase, and the Dust Bowl while encompassing political centers like Topeka, Lincoln (Nebraska), and Oklahoma City. The Plains intersect major transportation corridors including the Lincoln Highway, the Santa Fe Trail, and segments of the Transcontinental Railroad.

Geography and Boundaries

The Plains span large portions of Kansas, Nebraska, South Dakota, North Dakota, Oklahoma, Texas, Colorado, Wyoming, Montana, New Mexico, Iowa, Minnesota, and Missouri, bounded eastward by the Mississippi River and westward by the Rocky Mountains, with northern extents touching the Canada–United States border adjacent to the Canadian Prairies. Major physiographic subregions include the Great Plains, the Central Lowlands, and the Piedmont transition zones near Missouri River valleys and the Arkansas River. Prominent drainage basins such as the Missouri River and the Red River of the North define subregional hydrology, while interior features like the High Plains and the Black Hills create local relief.

Sedimentary strata deposited during the Cretaceous and Paleogene periods underlie the Plains, with thick deposits of Pierre Shale, Ogallala Formation, and other formations tied to the ancient Western Interior Seaway and later fluvial systems like the Missouri River and Platte River. The uplift of the Rocky Mountains during the Laramide Orogeny and subsequent erosion supplied vast amounts of sediment forming the High Plains and the Great Plains aquifer (also called the Ogallala Aquifer). Pleistocene glaciations associated with the Wisconsin glaciation sculpted the northeastern Plains, producing loess deposits linked to windborne material from the Mississippi River valley and contributing to soils catalogued under the Mollisol order used in regional soil surveys.

The Plains exhibit climatic gradients from humid continental climates in the north and east, typified by locations like Fargo and Sioux City, to semi-arid and steppe climates in the west and south near Amarillo and Lubbock, influenced by the Jet Stream and periodic El Niño–Southern Oscillation phases. Weather extremes include tornado alleys centered near Oklahoma City, Wichita, and Dodge City, and historical droughts such as during the Dust Bowl era. Vegetation zones transition from tallgrass prairie remnants near the Mississippi River to mixed- and shortgrass prairies across the High Plains, hosting ecoregions defined by agencies like the United States Environmental Protection Agency and the National Park Service.

Native plant communities include dominant prairie species such as big bluestem, little bluestem, switchgrass, and Indian grass in tallgrass zones, with shortgrass assemblages like blue grama and buffalo grass westward; riparian corridors support cottonwoods and willows found along the Platte River and Niobrara River. Faunal assemblages historically featured immense herds of American bison traversing corridors between places like Badlands National Park and the Tallgrass Prairie National Preserve, predators such as gray wolf and coyote, and avian migrations including prairie chicken and sandhill crane stopovers at wetlands like Cheyenne Bottoms and Quivira National Wildlife Refuge.

Indigenous nations including the Lakota, Dakota, Nakota (Assiniboine), Cheyenne, Arapaho, Comanche, Kiowa, Pawnee, Osage, and Otoe-Missouria maintained complex cultures across the Plains, engaging in bison-centric economies, horse cultures introduced after European contact, and diplomatic relations recorded in treaties like the Treaty of Fort Laramie (1868). European-American expansion accelerated after the Louisiana Purchase and events such as the Oregon Trail migrations and the construction of the Transcontinental Railroad, leading to conflicts including the Battle of Little Bighorn and policies enforced by institutions like the Bureau of Indian Affairs. New Deal programs responding to the Dust Bowl era involved agencies such as the Soil Conservation Service and initiatives like the Civilian Conservation Corps.

Agricultural transformation replaced vast native prairies with cropland and rangeland; principal commodities include wheat from areas like Kansas State University extension regions, corn in Iowa and eastern Nebraska, cattle ranching across Texas Panhandle and Nebraska Sandhills, and sorghum in Oklahoma. Irrigation draws heavily on the Ogallala Aquifer, affecting sustainability debates involving entities such as the U.S. Geological Survey, Natural Resources Conservation Service, and state water agencies. Farm policy influences via the Farm Bill and institutions like the United States Department of Agriculture shape commodity programs, conservation easements, and practices promoted by land-grant universities including Kansas State University, University of Nebraska–Lincoln, and Oklahoma State University.

Transportation networks across the Plains feature interstate highways such as Interstate 70, Interstate 80, and Interstate 35, major rail corridors operated historically by companies like the Union Pacific Railroad and BNSF Railway, and air hubs at cities like Denver International Airport (edge of the Rockies) and Kansas City International Airport. Energy industries include oil and gas plays in the Permian Basin and Williston Basin, wind energy developments across the Great Plains Wind Corridor near Amarillo, Abilene, and Garden City, and carbon sequestration pilots involving agencies like the Department of Energy. Urban growth centers such as Oklahoma City, Tulsa, Kansas City, Omaha, and Denver have driven metropolitanization patterns, while rural depopulation trends affect counties monitored by the United States Census Bureau.