The area was first inhabited by Goshute Indians. Their descendants continue to live on a reservation immediately to the west of the Deep Creek Range. In 1827 the explorer Jedediah Smith was the first known white man to traverse the region as he searched for a direct route across the Great Basin. Major Howard Egan further explored the area in the 1850's, as he assisted George Chorpenning with a U.S. mail contract between Salt Lake and California.

By 1858, Chorpenning had built a mail station at Pleasant Valley. The following spring an Indian farm was established by the government at Ibapah. Simultaneously, LDS missionaries were called to colonize and do missionary work among the Indians at Ibapah. Major Egan's Pony Express station was headquartered at Ibapah in 1860 and another major station was located thirty miles to the east on the other side of the Deep Creeks at Willow Springs (later named Callao).