The Dolores River was named by two Spanish Catholic priests, Francisco Anastio Dominguez and Silvestre Valdez de Escalante, as they passed through the area in 1776. On their journey to find a route from the missions of Santa Fe, NM to California, they discovered the river and called it "Rio de Nuestra Senora de las Dolores" or the River of Our Lady of Sorrows. Although their purpose was never completed, their visits were the first to be recorded, and they opened up the area for settlement. The ancestral Puebloans were the origional inhabitants of the area, living here until about A.D 1300. Historians are still trying to determine why they left the area, leaving behind a wealth of artifacts and remnants of their villages and kivas. They are believed to be the ancestors to the present-day Hopi Indians of Arizona and the Pueblo Indians of New Mexico.

The next to arrive were the Ute Indians whose migration routes took them through the Dolores River Valley and north, south east and west into northern Colorado, Utah, Arizona and New Mexico. Some of their descendants now live on the Ute Mountain Ute and Southern Ute reservations in Southwest Colorado and on the Uintah and Ouray Ute reservations in southeastern Utah. In 1859 the first Anglo expedition, headed by Newberry, a geologist, and J.N. Macomb, arrived here. According to the journal they published by Newberry, they came through the area on their way to the junction of the Grand (Colorado) and Green rivers.