The entrance to Slot Canyon is about 1/2 mile from the trailhead.
Finding Slot Canyon Trail, a 2.5 mile roundtrip hike through the desert and Robledo Mountains, can be difficult as it is not marked on maps of the Organ Mountains-Desert Peaks National Monument. There are no signs at the trailhead either. Its location seems to be a well-kept secret of the locals. However, once you have the correct clues, you can find the trail. It is located on the North Valley Drive out of Las Cruces, which is New Mexico Highway 185. The trailhead is just over 19 miles north of the city. When you pass the hamlet of Radium Springs you are getting close. Look for mile marker 19 on the right side of the highway. Just beyond that you'll find two large parking areas, one on each side of the road. The trail begins on the left side (west) of the highway.
The Slot Canyon Trail begins north of Radium Springs, mile marker 19, on the west side of Highway 185. This is in the Desert Peaks section of the national monument.
Finding Slot Canyon Trail is a cinch once you've reached the parking area on the west side of Highway 185. You will need to climb over the single green gate. This is completely legal as this is public property managed by the New Mexico State Land Office. The trail is visible to the southwest and it passes through a myriad of public lands- from the State Land Office, to the Bureau of Land Management, and finally to Organ Mountains-Desert Peaks National Monument. There are no signs marking any of this, but there are rock markers along the trail in the sandy areas. Just keep heading south, and then turn west when the canyon opens on the horizon. (top photo above)
This is the green gate to climb over to start the Slot Canyon Trail on the west side of Highway 185.
Heading into the opening of the canyon, the trail soon begins to narrow, and becomes very narrow as you enter the slot. Many places in the slot are only wide enough for one person. This section of the trail is dark and claustrophobic, but the slot is only about 1/4 mile long, so take some photos, walk briskly, and you'll soon be out of the slot and back into daylight. The slot was formed by water erosion many thousands of years ago. However, if the weather is threatening rain (very rare) on the day of your hike, it is best to come back to the slot another day as there is no escape from the slot if it floods.
It can be very dark in the slot, even on a bright sunny day as the steep walls all but block out the sky above.
The sun breaks through the darkness in this narrow section of Slot Canyon.
After emerging from the slot, hikers may continue the journey along the broad arroyo. In about 1/4 mile you will see a trail heading up the cliffs to the left. It is worth the effort to climb up this trail and observe the spectacular view of the slot below, and the Doña Ana Mountains off to the east. After ascending the peak, the trail continues on down to the right. This section is very steep and slippery. Trekking poles are helpful. Use caution, and eventually enter back into the arroyo, and head back to the slot for your descent back to the trailhead.
At the top of the peak above Slot Canyon, with the Doña Ana Mountains in the distance to the east.
For a video illustrating the Slot go here: https://www.youtube.com/watch?v=0eHIuF8EVN4