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 1 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

Geology

• Missouri Plateau, glaciated – east-central South Dakota, northern and eastern North Dakota and northeastern Montana
• Missouri Plateau, unglaciated – western South Dakota, northeastern Wyoming, southwestern South Dakota and southeastern Montana
• Black Hills – western South Dakota
• High Plains – eastern New Mexico, northwestern Texas, western Oklahoma, eastern Colorado, western Kansas, most of Nebraska (including the Sand Hills) and southeastern Wyoming
• Plains Border – central Kansas and northern Oklahoma (including the Flint, Red and Smoky Hills)
• Colorado Piedmont – eastern Colorado
• Raton section – northeastern New Mexico
• Pecos Valley – eastern New Mexico
• Edwards Plateau – south-central Texas
• Central Texas section – central Texas

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.