Agua Fria Mountain is a large mesa eighteen miles north of Terlingua in southwestern Brewster County (at 29°31' N, 103°39' W). Its steep, deeply cut and eroded sides rise some 1,500 feet above the surrounding Chihuahua Desert floor. Near its southeastern edge the mesa reaches an elevation of 4,828 feet above sea level. Its name, Spanish for "cold water," refers to a large spring at the base of a cliff several hundred feet high on the western side of the mountain. The spring is surrounded by willows and large boulders and harbors an abundant growth of watercress. The cliff forms a large protective overhang, beneath which are deep accumulations of ashes and burned rock, as well as numerous flakes of flint, obsidian, jasper, and chalcedony. Colorful pictographs cover the lower reaches of the cliff face and many of the nearby boulders. One modern historian of the region cites evidence of a rather extensive irrigation system built by American Indians to the north and northeast of Agua Fria Mountain. A camel train under the command of Lt. William Echols camped in 1859 at Agua Fria Mountain (see CAMELS). In the 1880s, Agua Fria Mountain was the northern extent of the G4 Ranch, one of the earliest and largest ranches in the Big Bend. The ranch maintained a line camp near the spring at the foot of the mountain. Agua Fria Mountain is clearly visible from State Highway 118, seven miles to the east.