OverviewTonuco Mountain (called San Diego Mountain on some maps) is a broad sandstone-capped peak that rises about 1,000 feet above the flood plain. It includes two small echelon uplifts, the Tonuco uplift and the West Seldon Hills uplift. Three main volcanic sequences are recognized in Tonuco Mountain: 1) about 2,000 ft of andesite flows and associated sedimentary rocks, 2) nearly 900 ft of rhyolite pebble breccia, and 3) sparse dikes of basaltic andesite. Mineral deposits in the Tonuco uplift consist of barite and fluorite occurring in thin discontinuous veins, mainly in Precambrian rocks. Human uses of geologic material include petroglyphs and tool making, mining for minerals.
This area is well known for a challenging Jeep trail, petroglyphs, mining and the Camino Real. In 1927, Congress granted the areas surrounding Tonuco Mountain to New Mexico State University and since that point in time the area has been known as "College Ranch".
Getting ThereMost New Mexicans have probably passed Tonuco Mountain numerous times as the drive south on I-25 between Hatch and Las Cruces. There are two ways to get to the general vicinity of Tonuco.
From the south (Las Cruces area), exit I-25 at Radium Springs (exit #19). Head east from the interstate for a about 0.1 miles and turn north on CR E070. Follow this generally good dirt road for about 9.5 miles north until the intersection with CR E071. Take CR E071 under the interstate and through a gate (Note: After rains the dirt underpass is often flooded). Turn left after passing through the gate and follow the dirt road about 0.75 miles until reaching a sandy wash at the foot of Tonuco. Be careful not to get your vehicle stuck in the deep sand of the arroyo.
From the north (Truth or Consequences area), exit I-25 at Upham (exit 32). Immediately get on a generally good dirt road that heads south and parallels the interstate. Follow this road for approximately 4 miles unti it veers off away from the interstate towards Tonuco Mountain. Continuing straight at this point will take you through a gate and under the interstate as described in the southerly approach. After veering right away from the interstate follow the road for about 0.75 miles until it enters a sandy wash. Park here, but be careful not to get stuck in the deep sand.
PetroglyphsArcheologists speculate that the Jornada Mogollon culture (1-1400 A.D.) may have used the areas surrounding Tonuco Mountain and the nearby spring as residential camps. This area could have provided a spot for the cultivation of simple crops. While hiking in the area keep an eye open for sherds of plain brown pottery and petroglyphs. There are 250+ petroglyphs in the area that date back to 1200-1300 A.D.
The Camino RealAlthough many Indian trails undoubtedly crossed the Jornada plain, the earliest trail for which there is evidence is the Camino Real, the route established by the Spanish between Chihuahua, Mexico and Santa Fe, New Mexico. The trail wound northward through the Mesilla Valley to a camping place called Robledo, near present-day Radium Springs. From there the route left the river valley and made a gradual ascent to the rim of the Jornada plain; there it turned northwesterly along the edge of the plain, continuing to another camping place called San Diego, in the vicinity of Tonuco Mountain. Most of the eight-mile distance between Robledo and San Diego was over land that is now part of the College Ranch.
The Camino Real carried nearly all traffic between Mexico and New Mexico for over 250 years. Traffic on the trail included several forms of animal-drawn transportation as well as flocks and herds of domestic livestock. Mesquite beans were a source of feed for the animals. Eventually, rows of mesquite bushes lined the trail, growing from undigested mesquite seed dropped by the livestock. Even in 1987 a sharp observer can see portions of the trail on the College Ranch,
still delineated by rows of mesquite bushes.
One of the earliest travellers on the Camino Real was Don Juan de Onate, agent for the Spanish Crown, who conducted a party of colonists, soldiers, and priests over the trail in 1598, on their way to establish the first Spanish colony, north of present-day Santa Fe. Two centuries later, Mexican independence opened the borders of New Mexico to trade with the United States. Josiah Gregg, author of Commerce of the Prairies, was among the first Americans to travel the Camino Real, taking six wagon-loads of merchandise to Chihuahua in 1839.
This section of the Camino Real was a welcome site to travelers heading south. It marked the end of the 90 mile section dubbed, Jornada del Muerto (The Journey of the Dead One). This section was nearly completely waterless and the welcome sight of the Rio Grande made a great impression on travelers.