Running the Maroon Bells Four Pass Loop in One Day

@July 17, 2020

Also known as the Maroon Bells - Snowmass Wilderness Loop, this route covers 27.1 miles of pristine mountain wilderness. It’s at high elevation — the majority of the loop is between 10,000 and 12,500 feet above sea level. The trail winds through four mountain passes, making the total elevation gain about 8,000 feet. Most people complete the loop over three or four days, which I’d love to do as well, but it’s also runnable in one day with preparation.

There are a couple of different sources for length of this route, ranging from 26 to 29 miles. We recorded 27.1 miles with Garmin GPS, starting from the parking lot near Maroon Lake Trailhead.


Most runners do the loop counter-clockwise. This puts the last two mountain passes close together, allowing you to finish most of the climbing earlier in the day. The counter-clockwise loop also ends with a seven-mile downhill at an easier grade than the start.

The Maroon Lake Trailhead is around 9,500ft above sea level, with the passes nearing 12,500ft.
The Maroon Lake Trailhead is around 9,500ft above sea level, with the passes nearing 12,500ft.

The route

We stayed in Snowmass, which is more affordable than Aspen but a bit farther away. Waking up at 4am, we were able to start from the Maroon Lake Trailhead at 5:30am. Starting this year, parking permits at the trailhead are required.

We reached the top of Buckskin Pass shortly after 7:00am. The first five miles leading up to Buckskin are rocky, steep, and mostly un-runnable, but the sunrise is worth it.

The view from Buckskin Pass, at 12,462 ft.
The view from Buckskin Pass, at 12,462 ft.

From Buckskin, the trail drops in elevation until reaching Snowmass Lake, about 9 miles in. The lake is probably the farthest you want to go if you’re considering turning around. Check to see if you’re making the right pace here to complete the loop before dark.

Snowmass Lake
Snowmass Lake

The most technical section comes right after Snowmass Lake. While the snow was well-tread in July, this part could easily have been impassible. Lightweight trekking poles are helpful. Winter hikes would require an ice axe and crampons — this is definitely a no-fall zone.

The snowy traverse following Snowmass Lake.
The snowy traverse following Snowmass Lake.

We reached the top of the second pass, Trail Rider, around 9:30am or 4 hours in. For comparison, the Fastest Known Time for the loop is currently 4 hours and 17 minutes (held by professional ultra-runner Morgan Elliot). While we were making an effort to run the straights and downhills, we weren’t too concerned with pace.

Trail Rider Pass
Trail Rider Pass

The descent from Trail Rider pass holds the longest runnable stretch of terrain. It also has the largest river crossing, which at the time was about 3-4 ft. deep. This is a great place to filter, since it’s about halfway through and the current is strong.

The climb up to the third pass, Frigid Air, is the hardest part of the loop. 16 miles in, you rise about 1,000 feet per mile over the course of two miles. We took this part as fast as possible as the skies darkened, reaching the top around 1:00pm. It’s best to avoid exposure above the tree-line during a storm, and if conditions had worsened, we likely would have waited it out from a lower elevation.

The ascent to Frigid Air Pass. The clouds were concerning, but the rain ultimately held off.
The ascent to Frigid Air Pass. The clouds were concerning, but the rain ultimately held off.

My favorite segment was the 2 miles between Frigid Air and West Maroon Pass. It’s still single-track, but not too steep or rocky. Just an easy, gradual downhill. The view of the valley below is incredible.

The valley below West Maroon Pass.
The valley below West Maroon Pass.

We reached the top of West Maroon Pass around 2:00pm, only one hour after descending Frigid Air. The ascent to West Maroon Pass is fairly quick since there’s not much of an elevation drop between the two passes.

From the top of West Maroon Pass.
From the top of West Maroon Pass.

It felt great to be at the top of the final pass with only 7 miles of downhill left to go. Unfortunately, the trail down is rocky, and only about half of it is runnable. We made it back to Maroon Lake Trailhead at 4:30pm, exactly 11 hours from our departure time at 5:30am.


Consolidated timeline

Maroon Lake Trailhead
Buckskin Pass
Snowmass Lake
Trail Rider Pass
Frigid Air Pass
West Maroon Pass
Maroon Lake Trailhead


I wore the Salomon ADV Skin 5, and was really happy with it. It can reasonably hold 2-2.5L of water between a 1.5-2L reservoir and 2 500mL bottles. The reservoir section is made of a stretchy fabric that can be used to stow a jacket, and there are pockets on the side for food or other things.

Personal gear

  • Sunglasses
  • Sunscreen
  • Trail shoes
  • Quick-dry t-shirt
  • Long-sleeve
  • Buff
  • Headlamp. Just in case it gets dark. Also helpful if you start in the dark.
  • Rain jacket. Afternoon storms are common in Colorado summers. We got hit with a bit of rain, but it ultimately held off.
  • Hat
  • Map + GPS map downloaded. I’d recommend using AllTrails or Gaia.

Group gear

  • Water filter. I carried 2.5L of water, and had drank about 2L by the time we reached the river crossing halfway in. A filter is definitely required.
  • Medkit. It’s pretty likely that someone will fall while running. Bring some bandages, Neosporin, etc.

Food & water

We carried around 2,200 calories each, and I ultimately ended up eating about 1,500. The uphills will burn a ton of calories! It’s helpful to eat something every hour and start with a large breakfast. Here’s what I brought:

  • 1.5L of water (with the expectation to filter another 1.5L)
  • 500mL of Roctane, 500mL of Maurten 320
  • Giant PB & J sandwich.
  • 3 Clif Bars. Ate two.
  • 2 GU Stroopwafels. Only ate one.
  • Trail mix. Didn’t eat.
  • Dried mangoes. Didn’t eat.

Closing thoughts

This was the longest run I’ve done, but the scenery and varied terrain along the trail made the hours go by quickly. There’s something about trail running that’s intimately relaxing. It requires enough focus on footwork to keep you in the moment and your mind off the pain. It’s piqued my interest in ultras, and while I haven’t made any commitments yet, I’m looking into some 50-milers for when races start again.