Hands down, the Four Pass Loop is one of the best hikes in Colorado. This four-day, three-night circuit takes in some of the most jaw-dropping scenery in the Rockies. And with four high-mountain passes and over 7,700 feet of elevation gain, you'll get a serious shot of vitamin L!

Planning any backpack is a pain in the ass, but the Four Pass Loop throws trailhead access, snowfields, creek crossings, and some tricky regulations into the mix. But never fear, this handy guide will provide all the beta you need for an effortless trip.

So happy trails, don't feed the bears, and feel free to pop any questions you have in the comments.

Four Pass Loop Stats

• Total Distance: 26.6 mi.

• Total Elevation Gain: 7,700'

• Starting Elevation: 9,580' (Maroon-Snowmass Trailhead)

• Max Elevation: 12,480' (West Maroon Pass)

When to Go

The Four Pass Loop backpacking season stretches from July to October.

In the early season, expect muddy trails, big creek crossings, and snow on the passes. On the bright side, you'll see far fewer people.

Wildflower bloom peaks in mid-to-late July.

Crowds fall off beginning in September, when the days are still long and warm and weather tends to be drier. In order to catch the best of the fall foliage, aim for mid-to-late September.

Regulations

Considering East Maroon Lake (where the Four Pass Loop begins) receives 300,000 visitors a year, the surrounding wilderness is still relatively free of red tape.As you read, keep in mind that regulations change. So before setting out, check the Forest Service website for the latest info.Here are a few rules to be aware of:

Bear canisters

They're big, bulky, and don't fit in overhead luggage. But they're now required on the Four Pass Loop, because they save bears' lives. (A bear that's learned to associate people with food is at higher risk of being killed.)

Don't feel like buying a canister for one hike? Rent one at Ute Mountaineering in Aspen. 2017 cost is $6–$8 per day, plus a $5 "sanitation" fee.

Self registration

Rather amazingly, the Forest Service hasn't implemented paid permitting on the Four Pass Loop (yet). To make your visit "legit," fill out a self-service permit at the trailhead or wilderness boundary. Tear off the "hiker" portion of the permit and carry it with you for the duration of the trip.

Additional rules

• Max group size is 10

• Dogs must be leashed

• Near Crater Lake, you must camp in a designated site

• In all other areas, choose campsites located 100 ft. (about 70 steps) from trails, lakes, and streams

Hazards

The Four Pass Loop isn't technically difficult, but it isn't Disneyland either. It's a true wilderness adventure that requires preparation and some basic backcountry skills.

Water crossings

In the early season (July), expect three to four large, fast-flowing stream crossings on the Four Pass Loop. To prepare, I recommend carrying river shoes and a pack towel and placing your sleeping bag and electronics in dry sacks.

This video by Dave at Clever Hiker has some great stream crossing how-to and safety tips.

Wildlife

As noted above, Colorado black bears are rarely aggressive toward humans. However, they will be thrilled to sniff out and carry off your food, which really sucks when you're days from the trailhead. To minimize the chance of an encounter, follow the bear canister regulations above.

Marmots, porcupines, and rodents love to chew on salty backpacks and trekking pole handles. (In 2015, we met one very sad guy who was carrying his backpack down the trail in his arms after a porkie chewed off both straps.) To protect your gear, take it in the tent at night. You can also use accessory cord to hang your pack off the ground.

Weather

Afternoon thunderstorms are common in the Rockies. To minimize lightning danger, try to cross passes before noon. Descend from passes and ridges if you see clouds building or towering. You can always try again when the storm passes.

Hypothermia is a major cause of wilderness emergencies in Colorado. Even in summer, prepare for strong winds, heavy rains, and freezing temperatures. Pack insulating layers, a winter hat, gloves, and rain gear.

Snow

Acute mountain sickness (AMS, or altitude sickness)

Elevations along the Four Pass Loop range from 9,580' to 12,480', which is plenty high enough to make you feel like crap! Symptoms of mild AMS include headache, tiredness, upset stomach, and trouble sleeping (basically, a bad hangover). While it's very rare in Colorado, AMS can progress to life-threatening lung or brain edema that requires emergency medical treatment.

To prevent altitude sickness, stay hydrated, keep your pace slow, make sure you keep eating. You can read more about AMS at altitude.org. Or check out my blog post on how to prevent altitude sickness.

Emergency Info

As much as you prepare, you just never know what's gonna happen in the backcountry. Here are some resources in case you run into trouble.

Search and Rescue

For emergency assistance, contact Mountain Rescue Aspen by calling 911 or 970-920-5310 (dispatch).

Search and Rescue services are generally free in Colorado, but hikers may be responsible for expenses related to medical evacuation. Check out this video for more information.

Also, if you hike in the Colorado backcountry, please support our volunteer search and rescue organizations by purchasing a $3 CORSAR Card. This isn't insurance; it's just a donation to ensure that these services remain free and available.

Emergency Room

The nearest 24-hour emergency department is at Aspen Valley Hospital, located at 401 Castle Creek Rd. in Aspen.

Urgent Care

For non-emergency care on weekends and evenings, head to After-Hours Medical Care located at 234 Cody Lane in Basalt.

Leave No Trace

As you'll see, the beautiful Four Pass Loop is in danger of being loved to death. To protect this gorgeous wilderness for future generations:

• Camp in established, well-worn sites within 100 feet (70 steps) of lakes or streams.

• Use backpacking stoves instead of campfires.

• Stay on trails, even when they're wet and muddy. Don't cut switchbacks.

• Carry out poo, or dig a proper cat hole at least 6 in. deep. Also, don't pee or poo within 100 feet of lakes or streams.

Want to be a true hero for our wilderness areas? Visit the Center for Outdoor Ethics to learn more about Leave No Trace principles. You can even take an online course.

Packing

For the most part, you can hike the Four Pass Loop with standard summer backpacking gear. Some additional items that may be useful in the early season:

• Ice ax

• Sturdy river sandals and poles for creek crossings

• Pack towel

• Dry sacks (for electronics, sleeping bag)

• Extra socks

And as mentioned above, don't forget your IGBC-certified bear canister!For more packing tips, check out my post on the 10 Essentials of hiking gear.

Maps and Nav

The Four Pass Loop crosses parts of the Snowmass Mountain and Maroon Bells USGS Quads. You can print custom maps of the route at Caltopo.com.

Access and Parking

The Maroon-Snowmass Trailhead is located about eight miles from Aspen at the end of Maroon Creek Rd. The road is closed to passenger cars from 8 a.m.–5 p.m. during summer and early fall.

Trailhead Parking

If you can time your arrival when Maroon Creek Road is open, you may be able to snag a parking spot in the small overnight lot near the trailhead. (Double check you're not in the day-use lot, or you'll come back to a big fat ticket.)

If the Ranger Station is open when you pass, you'll need to purchase a $10 overnight parking permit, payable with cash or check only.

Note that the Forest Service prohibits camping at the trailhead.

Shuttle Bus

If overnight parking is full, park at Aspen Highlands Village ($5/$10 weekdays/weekends) and take the Maroon Bells Bus Tour ($8 round-trip) to the trailhead. (Purchase tickets at 4 Mountain Sports near the bus stop.)

Warning: Shh, this is an honest-to-god bus tour. Singing and loud talking are not appreciated, as our group learned when the driver schooled us over the intercom.

Suggested Itinerary

People hike (or more like trail run) the Four Pass Loop in a day. But taking four days and three nights will give you more time to enjoy this once-in-a-lifetime trip.

This itinerary follows a clockwise direction, which saves the best scenery for last and the steepest trails for the downhill.

Just want the bare bones? Here's a no-nonsense Four Pass Loop trail narrative by the Forest Service.

Day One: East Maroon Lake to Tree Line

This is a short, relatively easy day. Take your time getting to Aspen, and then ride the Bus Tour to the trailhead at East Maroon Lake. (No singing.)

With 300,000 visitors a year, it's hard to call East Maroon Lake a wilderness. But don't freak out at the sight of the tour bus hordes, because the shutterbugs and popcorn eaters usually don't make it more than half a mile up the trail. (Also, they all think you're a badass with your massive backpack and ice ax.)

Start with the obligatory photo shoot of the Maroon Bells reflected in glacier-sculpted East Maroon Lake. The Maroon Bells are both Colorado 14ers. Their proper names are Maroon Peak (14163') and North Maroon Peak (14019').

About the Maroon Bells

A little way up the trail, you'll find the awkward "Deadly Bells" display. The Maroon Bells earned this gruesome rep in 1965 when eight climbers died in a series of accidents. As the plaque notes, these mountains "kill without warning." But calm yourself, they're probably not going to kill you on the trail below.

Random trivia: the red mudstone that makes the Maroon Bells look maroon is extremely weak. It therefore tends to crumble under climbers, making these some of the most deadly mountains in Colorado.

• 9 Not-So-Deadly Colorado 14ers you can totally climb

Continue up the trail toward Crater Lake. Getting tired of stepping over rocks? This trail actually skirts the ancient rock slide that dammed the stream and formed Crater Lake. (Edited: why do I always write damned when I mean dammed?)

Creek crossing crux

At mile 3.6, the trail crosses West Maroon Creek. This isn't a big deal most of the year. But in early July when the river runs high with snowmelt, this crossing can get spicy. (On July 4, 2015, it was briefly above my short-girl knees and moving fast.) Choose your crossing spot carefully and try to cross early in the day when flow is lowest.

(Depending on how far you hike on Day 1, you may hit a second stream crossing that's smaller and shorter than the first.)

Camp before you begin the big ascent to West Maroon Pass. There are no designated sites, but look for well-used spots approaching and just above tree line.

Day Two: Day of Two Passes

Good morning! Today is a big one, so hork down that oatmeal and get an early start.

West Maroon Pass

Your first task is to climb West Maroon Pass (12,480'). The trail above tree line isn't super steep, but may require bashing and sliding through dewy willows (ew). Follow the route up, to the right, and into the West Maroon Valley where the first pass comes into view.

Keep in mind that snow and mud linger near the top of the pass throughout July. (On July 5, 2015, we were able to scramble around a large snowfield near the summit without too much trouble.)

From West Maroon Pass, enjoy gorgeous views of the Maroon Bells, Pyramid Peak (14,018'), Belleview Mountain, and Treasure Mountain. For what it's worth, this is the highest point on the route by 18 feet.

Frigid Air Pass

Descend into the lush Halsey Basin to the junction with the Frigid Air Pass Trail. While the trail has been quiet for a few miles, this stretch is full of day trippers hiking between Crested Butte and Aspen.

Turn right at a trail junction near a small lake and begin the steep, switchbacking climb to Frigid Air Pass (12,415'). Catch your break and take in views of Fravert Basin, distant Snowmass Mountain (14,092'), Capitol Peak (14,130'), and the "backside" of the Maroon Bells. From this vantage, their eponymous red color is brilliant.

Descend into the Fravert Basin. About a mile after the pass, the trail dips below tree line. Look for campsites in the forest and crash for the night. (If you've got extra energy, there also nice sites by the waterfall and creek crossing described below.)

Day Three: Over Trail Rider Pass to Snowmass Lake

Feeling a little grumpy about slogging up the next pass? Well, pound some Starbucks VIA, because you're about to see a really spectacular waterfall. It comes into view as you switchback down the headwall to the valley floor.

Next, cross the stream at the base of the valley. In early summer, this stream can swell to 20 feet across. However, in July 2015, the water was flowing very slowly, which made for a stress-free crossing.

Continue up the valley, following signs for Trail Rider Pass. The entire route has gorgeous wildflowers, but some of my favorite were along this section.

Trail Rider Pass

About a mile from the crossing, begin the long, steep slog up Trail Rider Pass. You'll start out winding through an aspen forest and eventually emerge into a "false pass" on the tundra. There are a couple easy stream crossings in the tundra section. (You shouldn't need to take off boots, even in July).

Finally, you'll switchback up a rocky ridge to Trail Rider Pass (12,420'), where you'll be treated to beautiful views of Snowmass Mountain and Snowmass Lake. If there's any snow left, this is a great place to stop and make an angel.

At this point, it's just 2 miles and 1,400' feet of downhill hiking to Snowmass Lake, your camp for the night. By this point, we were getting tired, but the marmots and pikas kept us entertained. We also crossed some really fun (and potentially glissade-able) snowfields.

The campsite at Snowmass Lake is down a spur from the main trail. If the weather is clear, prepare to squee. It's probably one of the most beautiful camping spots in Colorado.

Day Four: Over Buckskin Pass to the Trailhead

All good things must finally come to an end. If you took the no-fun tour to the trailhead, be sure to start early, because the last bus from the trailhead to Aspen Highlands leaves at 4 p.m.

So tear yourself away from the morning views of Snowmass Mountain reflected in Snowmass Lake and return to the main trail to conquer your final pass. The first section of trail is swampy and wet, and bug spray may save your ass. Use a log bridge to make a dry crossing (finally!) of Snowmass Creek.

Next, spend a mile switchbacking up a thousand feet to a beautiful, grassy basin, where you'll have good views of the pass towering another thousand feet above you. So take a shot of sugar and continue your ascent.

Buckskin Pass

Hopefully you've got some camera batteries left after three days, because the views from Buckskin Pass (12,462') will give you nine heart attacks. Seriously, if you don't like this pass, you have no soul.

Turn one way, and the black, slightly sinister massif of Pyramid Peak (14,018') stares down at you. Next, do a one-eighty, and you're face to face with the horned "Batman" summit of Snowmass Mountain (14,092').

After your photo shoot ("you're a cheetah, a very sad cheetah"), begin one of Colorado's most glorious descents as you return to Crater Lake to close the Four Pass Loop. (In July 2015, we had to start by down climbing a small snow bench on the far side of Buckskin Pass.)

Once you're below the pass, descend a series of broad switchbacks while keeping your camera out. The impenetrable black fortress of Pyramid Peak is going to be in your face for a couple of hours. You'll also have great views of the Maroon Bells. Many people report sighting white mountain goats in this area.

Eventually, the trail drops into Minnehaha Gulch, then descends forested slopes to Crater Lake. From here, retrace the 1.7 miles to East Maroon Lake. Enjoy the stares of the tourists as you emerge filthy and stinky from the woods and board the bus for Aspen Highlands.

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Originally published July 3, 2017. Updated June 8, 2020.