Mt Cox from trailhead

Mt Cox from approach

This route is an entirely off-trail outing in the northern portion of the Chihuahuan Desert, about 9 miles from the border with Mexico. The summit is reported to receive only a few visitors each year. Navigation is straightforward as long as visibility remains good. There is a surprising amount of wildlife, particularly birds. The altitude gain is modest but in places the footing is awkward and progress can be slow. In his guidebook, Greg Magee recommends a scramble of both Cox Peak and the neighboring hill, Mount Riley.  This report only covers Cox Peak.

Driving Directions:

  • From University Ave in Las Cruces, enter I25 South towards El Paso
  • After 3.0 miles, merge onto I10
  • After 29.3 miles, having crossed into Texas, take Exit 8 for Texas Highway 178, also known as Aircraft Road. The frontage road that you will first merge onto is called South Desert Road.
  • After 0.7 miles on South Desert Road, turn right onto Texas Highway 178 West at a set of traffic lights.
  • After 2.9 miles, on reaching the border with NM, continue straight with the road becoming NM 136 South (also known as the Peter V. Domenici Highway).
  • After 5.8 miles, at junction that has no traffic lights (unlike previous junctions), go right onto NM Highway 9. There is a small road sign, but if you don’t see it and go past this junction you will come to Santa Teresa Port of Entry (border station) in less than 2 miles.
  • After 23.8 miles, go right onto County Road A005. This is a signed gravel road with an additional sign saying “Mt Riley” at the junction.
  • After 1.2 miles come to the Mt Riley ranch where there are two cattle gates. Open and go through the gates, remembering to close them once you’re past. This will leave you still on CR A005.
  • After 3.3 miles veer right at a Y junction onto County Road A007 (signed).
  • After 2.2 miles go right and park at the trailhead.

As usual, all the expressed milages describe the distance past the previous bullet point.  If you are thinking about hiking both Cox Peak and Mt Riley then an early start is advised. It would be  very easy to miss the signs for Rt 9 or the County Roads in the darkness. It  helps to have a clear idea of the mileage.


The mighty Camry at the trailhead. Note tank to the left and hillock to the right.

The mighty Camry at the trailhead. Note the tank at the left edge of the photo and small hillock of land to the right.

The trailhead is a pull-out beside a metal tank  on the southeast side of the road – on the right as you are going in. The trailhead is a patch of ground between the road and an adjoining arroyo. An earthen dam across the arroyo serves to create an impoundment and I was surprised to see a few inches of water in the bottom of this pool. Rising above the trailhead is a small hillock, about 60′ tall. There are several such hillocks in the vicinity, it pays to know which of these marks your car’s location.


  • Starting Elevation: 4300 ft
  • High Point: 4700 ft
  • Net Elevation Gain: 1400 ft
  • Distance: 5.8 miles
  • Maps: USGS Mt Riley


03 Cox Pk and Mt Riley from trailhead

Cox Peak (left) and Mt Riley (right) from trailhead

Cross over County Road A007 to the northwest and head towards the hills. Cox Peak is the closer of the two peaks while Mount Riley is further north. Both peaks look to be about the same height. Enter the desert on a cow path and continue for about 500 feet until you hit what looks like a berm.  The main arroyo has braided out here and this may be a piece of the old arroyo wall. Follow a clear path alongside this “berm” until it reaches the confluence of braids and the arroyo forms up. The bottom of the arroyo offers easy walking so there is good reason to stick with it.

Juniper snag at mid slope on ascent of southeast face.

Juniper snag at mid slope on ascent of southeast face.

Eventually, however, it is necessary to leave the stream bed and begin ascending the southeast face of Cox Peak. Leave the arroyo about 0.5 miles from the trailhead. Head directly towards what appears to be the highpoint of Cox Peak (it is actually just the SW shoulder), crossing a secondary arroyo in a few hundred feet and then follow an even smaller stream bed up the face. It appeared that the angle was shallower on the south side so I tended to err in that direction. The small stream beds become full of loose rocks, so look for a way to stay above them (although the footing is uncertain everywhere). At about 1.2 miles from the trailhead come to a prominent juniper snag. At this point you will begin to encounter numerous defoliating ledges that strew the land with piles of flagstones. Zig zag to avoid these as you rise to the southeast shoulder.

East Potrillo Mountains (southeast shoulder in mid-right

East Potrillo Mountains in the distance. The southeast shoulder of Cox Peak is the dark bump at mid-right.

Upon reaching the southeast shoulder, look up to the false summit and be glad that the day is no hotter. There are a few sparse alligator junipers for shade, it might be advantageous to rest here since there is precious little shade above you. Look back towards the trailhead and study the appearance of the cone that marks your car’s location for future reference. Also, note that there are several parallel arroyos going south from the mountains. On return you’ll want to strike the deepest of these to get directly back to the trailhead.To the east of the trailhead is a small range called the East Potrillo Mountains (a fault block, accounting for its linear arrangement of peaks).

View north from summit to Mt Riley summit

View north from summit to Mt Riley summit

Turn now and ascend to the false summit at 1.6 miles. The angle eases somewhat and the footing is a bit better than among the outcrops. From here is it a short and shallow hike to the true summit at 1.9 miles. I did not find a summit register. There are views to the Florida Mountains in the distant west, the Cookes Range in the distant northwest and closer in are the small cinder cones and maars of the West Potrillo Peaks. (Potrillo, by the way, is Spanish for “colts”).  Mt Riley’s ridge line is close-by to the north. Over that ridge line you will see the Organ Mountains and Las Cruces.  Close-by to the east are the East Potrillo Mountains, and beyond them views to Aden Crater and Kilbourne Hole. The Franklin Mountains make up the eastern horizon.

Summit post, Potrillo Volcanic Area in mid-distance and Florida Peaks on the horizon

Summit post, Potrillo Volcanic Area in mid-distance and Florida Peaks on the horizon

Descend from the summit on the ridge heading north – there is even a trace of a trail atop it. This ridge curves westward, strikes a shoulder at 2.2 miles and offers you a choice of rather steep descent lines down the west face. As on the southeast face, the steeper terrain seems to have numerous, exfoliating outcrops of light gray rocks which create poor footing. The more northerly edge of this face is heaped with brownish rocks the size of small boulders. Avoid them, as in some places they seem poised to roll. There is also more vegetation to deal with – lots of prickly pear and chaparral.  At 2.5 miles the slope begins to gentle. Turn north and descend towards the western end of the Mt Riley ridge.

Approach to southeast shoulder from saddle between Cox Peak and Mt Riley

Approach slope to the southeast shoulder  and false summit as seen from saddle between Cox Peak and Mt Riley

At roughly 3 miles from the trailhead, enter the broad saddle between the Mt Riley ridge and Cox Peak. If you were going to hike the Mt Riley ridge you would cross this domain to the north. Instead I turned east to the saddle point. This area, although unquestionably dry, seems to be better watered than the surrounding desert and the plant growth is much denser. Cattle paths appear. Rise to the saddle point at 3.4 miles. The border patrol seems to be doing regular helicopter patrols in this area. The number of birds was remarkable given how dry things are. A falcon, possibly a peregrine, was making life difficult for the numerous morning doves.

From the saddle point descend in a broad arc around the base of Cox Peak. I stayed slightly high on the flank of Cox Peak to get a good view of the arroyo options. The route becomes obvious as views open to the south at about 4.5 miles. Descend into the main arroyo for an easy trek back to the car.


Author in front of Cox Peak

Author in front of Cox Peak (southeast shoulder, false summit and true summit from left to right)

The weather was terrific on a sunny January day. This is a great winter time hike.

If you want to do both Cox Peak and Mt Riley then get here early. Better navigators and younger hikers will probably move faster than I did, but the sun sets early on everyone in January.


The Summit Post has a good photos and states that there was a register on Cox Peak (in 2007). They approached from the west rather than from the south. Depending on your destination this could be an interesting alternative. Especially, one of these photos shows the piles of loose rock that characterize the steeper sections of the west face and is worth a quick study.

Southern New Mexico Explorer describes more of the wildlife and some of the difficulties on the trail.

Ghosts Of The Southline shows pictures of a ghost town near Cox Peak. I must have driven by it but never noticed.