Backpacking the Famous Four Pass Loop in Colorado

Updated: Jul 20, 2023

With summer approaching quickly it is time to get excited about those long day hikes, camping trips and backpacking trips. Many big adventures require time to plan and train, so I am personally starting to think about summer now and hoping that gets me through the last of the winter weather. If you are visiting Colorado this summer, this quintessential backpacking loop may be on your list. The Four Pass Loop is a challenging but absolutely breathtaking multi-day backpacking trip through the Maroon Bells-Snowmass Wilderness. The trail traverses four mountain passes over 12,000 feet through the rugged Elk Mountain Range, providing views of some of the tallest and most striking mountains in Colorado, colorful wildflowers, and crystal clear alpine lakes.

I backpacked this trail in August 2021 with some friends and my dog. It was one of the hardest routes I have ever completed but also the most rewarding. The remoteness of this area makes the mountains even more prominent and stunning. While much of this article is curated based on my own experience on the trail, I have also researched and included the most up to date information for 2023 to help you plan your adventure.

Hike Statistics

28 miles

7,752 feet of elevation gain

Starting Elevation: 9,580 feet

Highest Elevation: 12,500 feet

Planning

Time of Year

Summer: July-September

*There is often snow on this route from October to June. Conditions are weather dependent and may change each year, make sure to check recent conditions and upcoming weather forecasts.

Permits

Starting in 2023 permits are required for overnight backpacking in this wilderness area. Permits are limited to two permits per person per calendar year. You will want to form a rough plan of where you want to camp each night, as you will need a permit for each spot. Check out the links below for more information. Permits are now available for Summer 2023 through recreation.gov website and are available until the day of your trip, pending availability. Being the first summer reservations are required I would expect permits to book quickly for summer weekends, similar to other wilderness areas in Colorado.

Hike Details

You can start this loop in Aspen, CO or Crested Butte, CO. Aspen is the more well-known starting point but it does require paid overnight parking for the duration of your trip and a shuttle ride to reach the starting point. The downside of this option is the cost of parking as well as timing of the shuttle. The shuttle only runs during business hours and requires a reservation on your way in. The timing restrictions on the shuttle don’t allow you to adjust your plan too much, especially if you hike faster than expected. The Crested Butte starting point allows you to start right from your car but does have limited parking spaces and has previously been buried by avalanche debris, adding additional miles to the route. The distance varies slightly based on which side you start on, with the Crested Butte side adding a few miles. The biggest variation is the order you will do the four mountain passes in.

When I did this trip I started in Aspen and completed the loop clockwise. If I did it again I would start in Crested Butte and hike clockwise. In my opinion, counterclockwise would be a much harder route but there are arguments for and against both options. I preferred to ease into the hike and do the easiest pass while my pack was full. But others have commented that they would rather start with the most difficult pass on fresh legs.

I completed the loop over four days. We hiked much faster than we planned and could have finished on day three but were limited by the shuttle schedule, so we spent one extra night out there and finished with only a few miles on day four. Four days is usually the longest people take to complete this loop. Some people, usually trail runners, complete it in one day. When I do it next I will aim for 2 nights and three days.

Let’s talk about each pass individually. This order is based on hiking from Aspen in a clockwise direction.

West Maroon Pass (12,490 feet)

This is the shortest and easiest of the four passes. It has a steady and gradual incline all the way to the top. The views from the top were stunning! It does get fairly crowded on top of this pass because a lot of people day hike from Crested Butte to Aspen, which crosses over this pass. There are water sources on both sides of this pass and ample campsites on the Aspen side. There are no campsites in between West Maroon Pass and Frigid Air Pass.

Frigid Air Pass (12,405 feet)

This pass has absolutely stunning views of Maroon Peak on top. It is much more challenging than West Maroon Pass; it climbs steadily but with a lot of incline gain. The last ¼ mile gets extremely steep. There was nothing technical about the climb but it was steep with loose rock making it quite exhausting. There were no water sources after the basin between West Maroon Pass and Frigid Air Pass until you were below tree line on the other side. You will want to make sure you have plenty of water before climbing this pass as it is exposed with no tree cover the entire time. There are no campsites in between West Maroon Pass and Frigid Air Pass but there are many campsites after you cross Frigid Air Pass and descend below the tree line. The valley below this pass, before Trailrider Pass, is called Fravert Basin and features many beautiful waterfalls and plenty of water sources.

Trailrider Pass (12,415 feet)

This pass was without a doubt the most challenging pass in the loop, the first half of the pass has almost 1000 feet of elevation gain in one mile and not much shade. It is a well maintained trail, not technical in any way, just long with sustained elevation gain the entire way. About half way up this pass there is the option to take a short detour, about 3 miles, to Geneva Lake. I highly recommend adding a few miles to your route for these breathtaking views. There are multiple campsites at this lake but you will likely be the only one there. If you take the detour you will have about half of the pass remaining afterwards, which is less steep than the first half. When you reach the top of the pass you get the first magnificent view of Snowmass Lake. As you approach the lake there is a rockfall along the route that blocks the trail. You will need to carefully traverse this section and keep an eye out for cairns and/or keep an eye on your GPS map. This pass ends at Snowmass Lake where there are many campsites, however they do fill up fast. There are a few creeks shortly after Snowmass Lake, which will be your last water source for a while.

Buckskin Pass (12,460 feet)

After Snowmass Lake you will head downhill for a while before starting your ascent up Buckskin Pass. This pass is challenging but more gradual than Trailrider Pass. It also has many sections of tree covered trail to offer shade. The final section is a series of switchbacks before you descend quickly over the other side into Minnehaha Gulch. At this point you could add another detour, about 4 additional miles, over Willow Pass to Willow Lake. We did not add on this detour but I will next time for another beautiful alpine lake. Willow Pass trail winds through aspen lined trails and would be even more beautiful in the fall. Buckskin pass offers quite a bit of shade on the way up and down as well as multiple water sources and ample campsites on both sides. On the far side, Aspen side, of Buckskin Pass there are many options for campsites.

Camping

You must camp in designated areas.
You must have overnight-permits for each night you plan to camp.
Camping is not allowed within 100 feet of all lakes, streams, and the trail.
Availability of water sources will vary significantly throughout the summer, I recommend reading recent views prior to your trip to plan your water refill stops. All water will need to be treated prior to drinking.
Campfires are prohibited in many areas of Maroon Bells-Snowmass Wilderness including within 100 feet of any water source or above 12,800 feet. Check the map when planning your campsites to understand these rules.

Other Rules and Regulations

Bear canisters are required for all backpackers in the Maroon Bells-Snowmass Wilderness
Have a plan for human waste. Human Waste Bags (WAG) are highly recommended. If you choose to not use these you must deposit human waste in holes 6-8 inches deep and at least 200 feet from the trail, campsites and water.
Group size is limited to 10 people.

Tips & Miscellaneous Information

You will be at sustained high altitude for this entire loop, it is important to understand the signs and symptoms of altitude sickness, as well as how to proceed if you experience them.
There is no cell phone service for the entire loop, I recommend carrying a satellite communication device such as the Garmin inReach Mini.
When at high altitude the weather conditions can change dramatically and quickly. Be prepared for all seasons and all weather.
Check recent reviews for trail conditions and water crossing information, consider bringing sandals for deep water crossings.

Dogs on the Trail

Dogs must be leashed at all times on this trail.
While there are many water sources, make sure you are carrying enough water for you and your dog.
The terrain on the entirety of this loop is very rugged, make sure you are equipped to handle injuries and fatigue. I highly recommend carrying paw coverage, booties, and a dog rescue harness such as the Pack-a-Paw Emergency Rescue Harness.
Be prepared to carry out all dog waste.
If your dog is carrying a backpack with their own food or water practice with the backpack, gradually increasing the weight over time, prior to the trip. A general rule of thumb is that dogs should not carry more than 25% of their weight.