The Continental Divide, "The Backbone of the Nation," follows the crest of the Wind River Range and then splits near South Pass, looping to create the Great Divide Basin before coming back together near Bridger Pass about 20 miles southwest of Rawlins. The scarce precipitation falling in the Great Divide Basin never flows out of Wyoming and escapes only by evaporation. Because no high mountains exist to the east or west, the Basin has ideal conditions for high winds that are generally restricted in mountainous areas, and these winds have produced extensive sand dune fields. The 90-mile-long Killpecker dune field is the largest continuous area of active sand dunes in the United States. Travelers along I-80 between Rock Springs and Rawlins cross the Continental Divide twice as they drive through the southern part of the Basin, once about 5.5 miles west of Rawlins near the Hadsell exit and again about 58 miles west of Rawlins between the Red Desert and Table Rock exits.