The Great Plains slope gently eastward from the foothills of the Rocky Mts. at an elevation of 6,000 ft (1,829 m) to merge into the interior lowlands at an elevation of roughly 1,500 ft (457 m). The 1,500 ft (457 m) contour line, the 100th meridian of longitude, and the 20-in. (51-cm) isohyet of precipitation are arbitrarily used to mark the region's transitional eastern border. In places, however, it is clearly marked by an escarpment. Much of the Great Plains was once covered by a vast inland sea, and sediments deposited by the sea make up the nearly horizontal rock strata that underlie the area. Intrusive igneous rocks account for sections of higher elevation. The Great Plains region has generally level or rolling terrain; its subdivisions include Edwards Plateau, the Llano Estacado, the High Plains, the Sand Hills, the Badlands, and the Northern Plains.
The Black Hills and several outliers of the Rocky Mts. interrupt the region's undulating profile. The Saskatchewan, Missouri, Platte, Republican, Arkansas, Cimarron, and Canadian rivers flow in wide beds, generally from west to east, and are important sources of water. Rainfall decreases from east to west. Except for its easternmost margin and the elevations, the Great Plains have a semiarid climate, averaging less than 20 in. (51 cm) of precipitation annually. There are wide seasonal temperature ranges and winds of high velocity. In the westernmost sections the chinook, a warm winter wind, brings relief from bitterly cold and snowy winters. The dominant type of vegetation consists of shortgrass prairies; trees grow in moister areas and along water courses.
Although overall the Great Plains are sparsely populated, with much of the grassland devoted to farms and ranches, about half the people live in small to medium-sized urban areas; Edmonton, Alberta and Denver, Colo. are the largest cities in the region. Soils throughout the region are fertile and very productive when water is available. The principal crop is wheat, concentrated in the Spring Wheat Belt (generally N of Nebraska), where the colder climate delays sowing until spring, and the Winter Wheat Belt (centered in Kansas and Oklahoma), where the milder climate allows for winter sowing. Other crops include sorghum, flax, and cotton. Cattle and sheep are raised throughout most of the Great Plains. Oil, natural gas, coal, and gold are among its mineral deposits.
The Great Plains were long inhabited by Native Americans, who hunted the teeming herds of buffalo (see bison) that roamed the grasslands and, due to wholesale slaughter by settlers and the U.S. army, were nearly extinct by the end of the 19th cent. The region was explored by the Spanish in the 17th cent. Until well into the 19th cent., the central Great Plains were called the Great American Desert. The first westward-bound pioneers bypassed the Great Plains. The railroads were largely responsible for their development after the Civil War. An initial wave of settlement was followed by emigration in times of drought. By the mid-1930s, decades of overgrazing and poor soil management in many of the Plains states had resulted in dust storms and the devastation of crops (see Dust Bowl).
See W. P. Webb, The Great Plains (1931, repr. 1981); N. R. Peirce, The Great Plains States of America (1973); B. W. Blouet and F. C. Luebke, ed., The Great Plains: Environment and Culture (1979).
The Great Plains are the broad expanse of prairie and steppe which lie east of the Rocky Mountains in the United States and Canada. This area covers parts of the U.S. states of Colorado, Kansas, Montana, Nebraska, New Mexico, North Dakota, Oklahoma, South Dakota, Texas and Wyoming, and the Canadian provinces of Alberta, Manitoba and Saskatchewan. In Canada the term prairie is more common, and the region is known as the Prairie Provinces or simply "the Prairies".
Some current thinking regarding the geographic location of the Great Plains is shown by a map at the Center for Great Plains Studies at the University of Nebraska-Lincoln. It extends the eastern boundary of the Great Plains down the Assiniboine River to Winnipeg, Canada, southward down the Red River of the North to South Dakota’s and Nebraska’s eastern border then down the Missouri River to Kansas City, down the eastern border of Kansas to Oklahoma where it breaks southwest toward Oklahoma City before continuing south through Ft. Worth and central Texas then west toward the Big Bend of the Rio Grande River. The region is about east to west and north to south. Much of the region was home to gigantic buffalo (American bison) herds until they were hunted to near extinction during the mid/late 1800s. It has an area of approximately 1,300,000 km2
The Great Plains are the westernmost portion of the vast North American Interior Plains, which extend east to the Appalachian Plateau. The United States Geological Survey divides the Great Plains in the United States into ten physiographic subdivisions:
The High Plains is used in a related, more general context to describe the elevated regions of the Great Plains, which are primarily west of the 100th meridian. The 100th meridian roughly corresponds with the line that divides the Great Plains into an area that receive 20 inches (500 mm) or more of rainfall per year and an area that receives less than 20 inches (500 mm). In this context, the High Plains is semi-arid steppe land and is generally characterized by rangeland or marginal farmland. The region is periodically subjected to extended periods of drought; high winds in the region may then generate devastating dust storms.
During the Cretaceous Period (145-65 million years ago), the Great Plains was covered by a shallow inland sea called Western Interior Seaway. However, during the Late Cretaceous to the Paleocene (65-55 million years ago), the seaway had begun to recede, leaving behind thick marine deposits and a relatively flat terrain where the seaway had once occupied.
In the next one hundred years the fur trade injected thousands of Europeans onto the Great Plains, as fur trappers from France, Spain, Britain, Russia and the young United States made their way across much of the region. With the Louisiana Purchase in 1803 and subsequent Lewis & Clark Expedition in 1804, the Great Plains became more accessible. A major fur trading site was located at Fort Lisa on the Missouri River in Nebraska. This type of early settlement opened the door to vast westward expansion, with settlements rising across the Great Plains.
The Homestead Act of 1862 provided that a settler could claim up to 160 acres (65 hectares) of land, provided that he lived on it for a period of five years and cultivated it. This was later expanded under the Kinkaid Act to include a homestead of an entire section. Hundreds of thousands of people claimed these homesteads, sometimes building sod houses out of the very turf of their land. Many of them were not skilled dryland farmers and failures were frequent. Germans from Russia who had previously farmed in similar circumstances in what is now Ukraine were marginally more successful than the average homesteader. The Dominion Lands Act of 1871 served a similar function in Canada.
The region roughly centered on the Oklahoma Panhandle, including southeastern Colorado, southwestern Kansas, the Texas Panhandle, and extreme northeastern New Mexico was known as the Dust Bowl during the late 1920s and early 1930s. The effect of the drought combined with the effects of the Great Depression, forced many farmers off the land throughout the Great Plains.
From the 1950s, on, many areas of the Great Plains have become productive crop-growing areas because of extensive irrigation. The southern portion of the Great Plains lies over the Ogallala Aquifer, a vast underground layer of water-bearing strata dating from the last ice age. Center pivot irrigation is used extensively in drier sections of the Great Plains, resulting in aquifer depletion at a rate that is greater than the ground's ability to recharge.
The rural Plains have lost a third of their population since 1920. Several hundred thousand square miles of the Great Plains have fewer than six persons per square mile—the density standard Frederick Jackson Turner used to declare the American frontier "closed" in 1893. Many have fewer than two persons per square mile. There are more than 6,000 ghost towns in the State of Kansas alone, according to Kansas historian Daniel Fitzgerald. This problem is often exacerbated by the consolidation of farms and the difficulty of attracting modern industry to the region. In addition, the smaller school-age population has forced the consolidation of school districts and the closure of high schools in some communities. This continuing population loss has led some to suggest that the current use of the drier parts of the Great Plains is not sustainable, and propose that large parts be restored to native grassland grazed by buffalo, a proposal known as Buffalo Commons.
The Great Plains contribute substantially to wind power in the United States. In July 2008, oilman turned wind-farm developer, T. Boone Pickens, called for the U.S. to invest $1 trillion to build an additional 200,000 MW of wind power nameplate capacity in the Plains, as part of his Pickens Plan. Pickens cited Sweetwater, Texas as an example of economic revitalization driven by wind power development. Sweetwater was a struggling town typical of the Plains, steadily losing businesses and population, until wind turbines came to the surrounding Nolan County. Wind power brought jobs to local residents, along with royalty payments to landowners who leased sites for turbines, reversing the town's population decline. Pickens claims the same economic benefits are possible throughout the Plains, which he refers to as North America's "wind corridor."
The Great Plains are part of the floristic North American Prairies Province, which extends from the Rocky Mountains to the Appalachian mountains.
Common mammals in the great plains are ground squirrels, prairie dogs, and rabbits. The swift fox was once very common, but humans have almost caused them to be extinct. Poisoning and hunting meant to kill wolves and coyotes often inadvertently harms the swift fox, and its habitat is rapidly being destroyed by humans.