Great Plains once meant High Plains, not a map label
East of the Rockies, North America’s Great Plains stretch about 500 miles east–west and 2,000 miles north–south across prairie and steppe—some 500,000 square miles. The name only stuck after Nevin Fenneman’s 1916 physiography; earlier writers said High Plains.
The belt covers Kansas, Nebraska, and the Dakotas almost entirely, plus eastern Colorado, Montana, and Wyoming, pieces of New Mexico, Oklahoma, and Texas, and sometimes western Iowa, Minnesota, and Missouri. Canada’s share is southern Alberta, Saskatchewan, and Manitoba, though Ottawa’s maps rarely print the label, and a trinational environmental atlas from a NAFTA agency uses it for a prairie ecoregion.
Structurally the plains are nearly horizontal strata running west from the 97th meridian to the foot of the Rockies, 300 to 500 miles across. The mountain front makes a sharp western edge, but the eastern edge is climatic, following roughly the line of 20 inches of yearly rain. The USGS splits the American portion into ten subdivisions, among them the glaciated Missouri Coteau and the High Plains with Nebraska’s Sand Hills and the Llano Estacado.
North of latitude 44°, small mountain groups break the surface; the Black Hills of western South Dakota rise like an island, an oval about 100 miles long and 50 wide. Between 44° and 42° lie the Badlands, where fine Tertiary sediments let every rill cut its own little valley after rain. The central section, in eastern Colorado and western Kansas, is a dissected plain of gravel and sand once spread by rivers from the mountains.
The northern plains owe their smoothness to rivers stripping away loose gravel, while the southern plains owe theirs to gravel laid down from outside. Bison dominated until mass slaughter in the later nineteenth century. Namesake species include the soapweed yucca, called Great Plains yucca, and the nonvenomous Great Plains rat snake, found from Missouri and Nebraska south into Texas.
Source: Great Plains
