Map by Joseph E. Forks
El Paso County is a small county (compared to the rest of the Trans-Pecos), lying at the extreme western tip of Texas. It consists of 1,057 square miles, predominately in the valley of the Rio Grande River, where large deposits of Quaternary sands exist. There are two mountain ranges in the county, the Franklins and the Huecos; only the Huecos are known to support alterna. The The Huecos are predominately Paleozoic Limestones, with several Tertiary Igneous intrusives, the most notable of which is contained in Hueco Tanks State Park.
El Paso County is truly a desert county, with its average rainfall at only 7.8 inches. Predominate plant life includes a variety of desert grasses, cacti, and shrubs (including mesquite, acacia, and creosote). Lechugilla and sotol are present in the mountainous areas.Population
El Paso is the most densely populated county in the Trans-Pecos region, with 612,546 people living mostly in the environs of El Paso. Additionally, there are numerous farming communities along the Rio Grande, including: Anthony, Vinton, Canutillo, Clint, Fabens, and Tornillo. Additionally, the Fort Bliss Military Reservation makes up much of the northern part of the county.Popular L. alterna Localities The Hueco Moutains along US 62/180
have produced a total of four alterna in the past 30 years, only one (two?) of which were actually in El Paso County. Formerly, more of this area was accessible to the public; however, a private gasline road which was once open to the public has recently been closed.
Collectors have long speculated as to the apparent absence of L. alterna from the Franklin Mountains, particularly since other species typically associated with L. alterna are common here, including Rock Rattlesnakes, Trans-Pecos Ratsnakes, and Lyre Snakes. Apparently, the Hueco Bolson (the valley just to the west of the Hueco Mountains) is a boundary too great for L. alterna to cross.