The San Rafael River, the life blood of the county, originates in the Wasatch Plateau where the headwaters are stored in several reservoirs for agricultural and industrial use. It flows into Castle Valley in three branches--Huntington Creek, Cottonwood Creek, and Ferron Creek--which unite to form the San Rafael River after they pass the communities and adjacent farm land. It then twists its way through the rock and desert to its junction with the Green River.

Occupation of the San Rafael region dates back thousands of years to include people of the Desert Archaic Culture who were followed by those of the Fremont Culture who inhabited present-day Emery County from about A.D. 500 to about A.D. l300. Evidence of these people can still be found in numerous pictograph and petroglyph panels, such as those in Temple Mountain Wash, Muddy Creek, Ferron Box, Black Dragon Canyon, and Buckhorn Wash-all sites listed in the National Register of Historic Places. In historic times Ute Indians occupied sites in Castle Valley, and travelers along the Old Spanish trail also passed through the present county.