In 1823, the US Government created a map labeling this area “The Great American Desert” , considering the area uninhabitable and unfit for agriculture. Settlers during the mid 19th century found this untrue after discovering the region was sitting on top of the world's largest water supply, the Ogallala Aquifer. Lying under eight states, this underground water supply turned this huge semi-arid expanse into an area that now produces one-fifth of the United States' wheat, corn, cotton, and cattle. Once thought to be a limitless supply of water, it is now understood that the aquifer is being drained faster than it is naturally replenished. Parts of Kansas, New Mexico, Oklahoma, and Mexico have seen the water level in the Ogallala Aquifer drop 100 feet since irrigation began, and parts of northern Texas. It will take thousands of years to restore the aquifer to its original levels.
For more information, research, and discussions about the Ogallala Aquifer, see the following links.