The Hueco Mountains are a range of mountains that rise in southern Otero County, New Mexico and extend 27 mi south into Texas, generally along the El Paso–Hudspeth county line just east of the city of El Paso, Texas. The highest point of the range is the Cerro Alto Mountain 6703 ft in Hudspeth County. The Hueco Bolson, a down-dropped area with an elevation of 4000 ft above sea level, with sedimentary fill nearly 9000 ft thick, lies between the Hueco and Franklin Mountains. Shallow, stony soils in the Hueco Mountains support oak, juniper, and some mesquite. The mountains were part of the Rocky Mountain trend, forced upward as part of the Laramide mountain-building period during the late Cretaceous, 60 to 70 million years ago. The word hueco is Spanish for hollow, gap, or hole.