In 1853 Captain John Williams Gunnison headed a railroad survey attempting to chart a route for a transcontinental rail line. Following the Spanish Trail, the party forded the Green River and reached the San Rafael Reef. Gunnison wrote, "As we approached the river yesterday, the ridges on either side of its banks to the west appeared broken into a thousand forms--columns, shafts, temples, buildings, and ruined cities could be seen, or imagined, from the high points along our route."

Soon after leaving the Swell, the explorers split into two groups for separate investigations. Gunnison and his party were attacked by Indians on 26 October 1853 while camped beside the Sevier River in central Utah. Gunnison and six others of the twelve men in that group were massacred.

Just before the end of 1853, John Charles Frémont led an expedition into the region, also searching for a railroad route. At the Reef, they turned south and worked their way along its towering wall. Then they lost their way in the deep snows of the Aquarius Plateau. Starving, they cached all their equipment and made a dash for Parowan. They were rescued by a band of Ute Indians and led into the settlement, having lost one man.