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Running the Four Pass Loop in a Day

The Four Pass Loop is one of the best backpacking loops in North America. We tackled it in a day.

The Four Pass Loop has a strong argument for being one of the most stunning loops in North America. Located outside of Aspen, Colorado, the loop hits four high passes -- Buckskin (12,462'), Trail Rider (12,415'), Frigid Air (12,500'), and West Maroon (12,490'). Most people choose to backpack it in 2-4 days. We decided to run it in a day (a fairly "common" thing for Colorado trail runners).

Quick facts:

  • The Four Pass loop is a 27 mile loop trail with about 8,000 ft of elevation gain. It traverses the Elk range, ascending and descending four passes over 12,000 ft.
  • It can be done clockwise or counter clockwise -- we chose to go counter-clockwise, starting with the steepest ascent, and taking advantage of the easy transition between Frigid Air and West Maroon later in the day.
  • Parking at Maroon Lake requires reservations (info here)

When is the best time to do the Four Pass Loop?

The best time of year to do the loop is typically June-October, although you'll need to be very weather-aware in the fall as snowstorms can hit early in the fall. The Maroon Bells road is usually open for the season from mid-June. During the summer months, be sure to watch forecasts for potential thunderstorms, as the weather can change quite rapidly in Colorado at any time of the year, leading to big temperature swings between low and high points.

Pack list for the Four Pass Loop

We were trail running, so I packed quite light. Here's a few key items from my kit:

  • Salomon Advanced Skin 12 - An excellent, all purpose running vest. While there are smaller, lighter versions, I like the 12 because the extra size means I can carry more stuff (if I want to).
  • Hoka Speedgoat EVO - Hoka has since phased these out, and I typically wear the my Speedgoat 5s
  • Salomon soft flasks (2x) with the Salomon XA filter cap - Love this little filter.
  • Gels and snacks

Our day on the loop

Our first challenge of the day was Buckskin Pass (and an early start). We hit the trail in the dark around 5:30 and quickly gained altitude up towards the pass, gaining 3,000ft in the first 4.5 miles. We caught sunrise just at the top of the pass, with views east of Pyramid Peak, and west towards Snowmass and Capitol Peak.

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Pyramid Peak

After cruising our first downhill of the day, we reached Snowmass Lake and stopped for a quick refill on water. This is an extremely popular camping area for folks climbing Snowmass or backpacking the Four Pass Loop. 9 miles down.

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Snowmass Lake

From Snowmass Lake, the trail winds upwards to Trail Rider. We were feeling great at the top of pass 2/4, Trail Rider Pass. 11 miles down. And time for a long down, and and long way back up to Frigid Air.

The view from Trail Rider Pass

Fravert Basin is simply one of the most stunning places I've ever hiked/ran. It was a long grind to re-gain the elevation we lost, but it was offset with these wild landscapes and views around every turn. You get views of the backside of the Maroon Bells (the most photographed peaks in CO), and this wide basin was so full of color that you forgot about how tired you were. Mostly. The climb up to Frigid Air Pass is pretty brutal as you're coming up on 18 miles. Thank goodness for the burrito I brought. And the Snickers.

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Fravert basin

It felt like we were "over the hill" at this point. 3/4 done, only one pass to go and not a ton of mileage left. The descent off of Frigid Air was just as gorgeous as the ascent. Luckily, you don't lose too much elevation here, as the trail descends and then traverses across towards West Maroon.

Descending Frigid Air Pass

The ascent up West Maroon Pass is short, but taxing. Tired legs were definitely coming into play by this point. It was a special moment to reach the top and see the long descent back down to the trailhead. A long, rocky downhill brought us back the the car (and crowds) at Maroon Lake. What a perfect day in the alpine. Great weather, great crew, incredible views. This has been on my Colorado bucket list for a long time so it felt good to check it off. It was my longest day out, and my longest trail run so far.

The Maroon Bells

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I'm Kyle Frost. Join 65,000 readers enjoying Here & There, my weekly outdoor/travel newsletter with nuance, questions, and complexity.