The Lower Black Box is a difficult but extremely rewarding hike through a beautiful water-filled canyon in the heart of the San Rafael Swell. The nearly 12-mile route winds through rugged desert terrain before descending a narrow water-filled canyon full of challenging obstacles. This hike is only recommended for experienced hikers in excellent physical condition with good navigation skills. Children should not attempt this hike.


The hike to the Lower Black Box begins at a remote trailhead in the northern San Rafael Swell (38.965799,-110.470056). A high clearance 4WD vehicle is required to access the trailhead on a network of extremely rugged dirt roads. A good map and off-road driving skills are essential.

From Green River, Utah:

  1. Drive west on Interstate 70 for approximately 31 miles and take exit 131 signed for Temple Mountain Road.
  2. After exiting, turn right (north) onto Buckhorn Draw Road.
  3. Drive 5.7 miles on Buckhorn Draw Road and turn right at the junction near Sinkhole Flat (38.929494,-110.601072).
  4. Drive 1.8 miles and turn left at the first major junction (38.916504,-110.574888).
  5. Continue 6.3 miles, passing two significant junctions: one on the left and another on the right, before arriving at a third junction at 38.963776,-110.515941.
  6. Turn right and drive 3.3 miles to the trailhead at the end of the road (38.965799,-110.470056).

The Hike

In addition to having good navigation skills and being in excellent physical condition, a hike through the Lower Black Box requires a great deal of advance planning. The route should only be attempted in ideal conditions when the water is low enough and warm enough to allow safe passage. Ideal water flows for completing this hike are around 25 cubic feet per second (CFS). Do not enter the canyon if flows are near or in excess of 50 CFS. Current river data may be accessed on the USGS website by checking river gauge number 09328500, called “SAN RAFAEL RIVER NEAR GREEN RIVER.”

Aside from seasonal water flow fluctuations, flash floods from storms are also a major concern. The San Rafael River is at the heart of a huge catch basin. Skies may be blue and clear near the trailhead while unseen storms in the distance send raging floodwater down the canyon. Several lives have been lost in this canyon as a result of high water. Do not enter the Lower Black Box if flood conditions are present or if precipitation is forecasted within the drainage area.

Water temperature is also an important factor to consider on this hike. Even on a warm day, the water deep in the Lower Black Box may be frigid. Hours of this hike are spent directly in the water swimming and climbing through waterfalls, making hypothermia a real threat. Very little sunshine gets through to the canyon floor and no escape is possible.

While no technical equipment is usually required, you will need to pack a few extra items for this trip. Sturdy wading shoes are a necessity and trekking poles or a walking stick can be very helpful. Everything you carry will get wet so bring dry bags for anything that must stay dry. A short length of rope or webbing may also come in handy.

From the parking area, begin hiking east through a gate on an old dirt road that is closed to motor vehicles. The road is easy to follow until it ends at a dry wash bottom, about 1.5 miles from the trailhead. Continue down the wash for 0.5 miles before arriving at the San Rafael River (38.972195,-110.444374).

CAUTION: Pay careful attention to the flow and temperature of the San Rafael River before proceeding. Anything more than ankle to calf deep water here could equate to very hazardous conditions within the canyon. If the water feels too cold, turn back. The descent through the Lower Black Box requires sustained swimming and wading in this water for several hours. Hypothermia is deadly and can strike quickly and without warning.

Before moving on, look around and take note of the landscape here at the river’s edge. This is the exit point you will need to watch for at the end of the hike and it can be easy to miss. Cross the stream and find your way through the dense foliage on the other side. From here, the route follows a network of social trails that traverse the east rim of the Lower Black Box. The trail can be a little tricky to follow in a few places and may require some advanced route finding skills.

Continue along the rim as the trail winds along the base of the San Rafael Reef, occasionally offering a glimpse of the Lower Black Box below. About 4.5 miles from the trailhead, a formation known as Swasey’s Leap becomes visible on the canyon rim below (38.989969,-110.466573). Legend has it that in the 1800’s, a local rancher named Sid Swasey, once jumped his horse across this narrow point to settle a bet with his brother, Charley. The successful jump purportedly earned Sid the ownership of Charley’s half of the cattle they were herding. The gap between canyon walls at Swasey’s Leap is around 10-15 feet wide and upwards of 60 feet above the river below.

Continue hiking on the rim past Swasey’s Leap until the cliffs end, offering easy access to the river below near the foot of Mexican Mountain. The distance from here to the bottom of the Lower Black Box where you first crossed the river is approximately 4.5 miles, however due to the extremely strenuous terrain ahead, it may feel like two or three times that distance by the time you are there. Now is a good time to take stock and make sure you are ready for the challenge ahead. If the river is running too high or too cold, or if you are not feeling 100%, turn back now. The Lower Black Box can be one of the best hikes you’ll ever do or one of the worst. If conditions aren’t right, or you are already feeling at all worn out, do not proceed. Several lives have been lost in this canyon.

Begin hiking down the canyon as the walls grow taller and close in on the river. It may be tempting to try to stay out of the mud and water at first, but don’t bother. The next 4.5 miles of the hike are spent directly in the watercourse and staying dry is not an option. After a few hundred yards, Swasey’s Leap is visible above. From here the canyon stays narrow with beautiful, blackened sandstone walls rising high on each side.

Work your down the canyon, hiking, crawling, swimming, and climbing through massive boulders, log jams and rushing waterfalls. Long stretches of deep water necessitate a great deal of swimming, but compared to the effort to get past the other obstacles, swimming might come as a welcome break. At times it is much easier to just float through the water rather than struggle through the ankle-deep mud and the countless submerged boulders along the way.

About 3 miles down river from Swasey’s Leap, the canyon widens and the walls give way to dense vegetation. Walking on the riverbank becomes possible at times, making travel down canyon slightly easier. Keep an eye out for the interesting sulfur springs along the river where clear, bubbling water flows up from the usually brown, murky stream.

Approximately 4.5 miles from the top of the Lower Black Box, or 9.5 miles from the trailhead, the river returns to the point where you first crossed it near the beginning of the hike (38.972195,-110.444374). Exit the river on the right and retrace your steps up the wash to the old dirt road, eventually leading back to the parking area. Total hiking distance is approximately 11.5 miles.

NOTE: The distance through the Lower Black Box is only a small portion of the overall hike but takes considerable time due to the rugged terrain and numerous obstacles. Plan on at least 8-12 hours to complete the entire route.

Rules and Regulations

  • No littering.
  • Pack out all trash.
  • Motor vehicles must stay on designated roads.

Special Considerations

  • Under ideal conditions and with the right skills, equipment, and preparation, this hike is extremely difficult. Under less than ideal conditions or with poor planning, this hike can become deadly in an instant. Several lives have been lost here. Read this trail description carefully and be sure all required elements are in place to complete the hike safely.
  • Like any desert canyon, the terrain inside the Lower Black Box can change dramatically from season to season and after floods. Do not go down anything that you cannot easily climb back up. Check with the Bureau of Land Management for current conditions before attempting the hike.
  • Pack plenty of water for the hike. The San Rafael River is too salty and mineral-rich to be filtered.


This trail guide is provided by Backcountry Post.