i don't know the answer but mabye this might help Great Plains, also called Great American Desert , major physiographic province of North America. The Great Plains lie between the Rio Grande in the south and the delta of the Mackenzie River at the Arctic Ocean in the north and between the Interior Lowland and the Canadian Shield on the east and the Rocky Mountains on the west. Their length is some 3,000 miles (4,800 km), their width from 300 to 700 miles, and their area approximately 1,125,000 square miles (2,900,000 square km), roughly equivalent to one-third of the United States. Parts of 10 states of the United States (Montana, North Dakota, South Dakota, Wyoming, Nebraska, Kansas, Colorado, Oklahoma, Texas, and New Mexico) and the three Prairie Provinces of Canada (Manitoba, Saskatchewan, and Alberta) and portions of the Northwest Territories are within the Great Plains proper.
