Mapped by the U.S. Government in 1849 for gold seekers and settlers, the Sand Hills had long been known to Indians and many Spanish explorers. This one hundred-mile belt of sand lies in Winkler and four other Texas counties and in New Mexico. Its width varies from three to twenty miles, and its outer dunes are held by dwarf oaks. Water at a depth of two feet supports willows, cottonwoods, and a plum thicket that provided food to early settlers. Many dunes rise more than seventy feet high, and the heavy, shifting sands formed a natural barrier to travel. The area also served as a campsite and game reservation for Indians, and it is now part of expansive cattle ranges and rich oil fields.