The shortgrass prairie ecosystem of the North American Great Plains is a prairie that includes lands from the eastern foothills of the Rocky Mountains east to Nebraska and north into Saskatchewan, including rangelands in Alberta, Wyoming, Montana, North Dakota, South Dakota, and Kansas, and extending to the south through the high plains of Colorado, Oklahoma, Texas, and New Mexico.These rangelands were formerly maintained by grazing pressure of American bison, the keystone species; the dominant grasses are blue grama (Bouteloua gracilis) and buffalograss (Bouteloua dactyloides).