Four-Pass Loop Guide: How to Hike This Classic Colorado in One Day

The Four Pass Loop: An Overview

The Four Pass Loop is one of Colorado’s most celebrated backcountry routes—a crown jewel in a state full of them. That’s saying something, given the state’s 58 fourteeners and 23 million acres of public land. Colorado literally has more hiking trails than suburban sidewalks. What makes the Four Pass Loop stand out is a rare trifecta: relative accessibility, intermediate technical difficulty, and jaw-dropping alpine scenery.

The route starts at the Maroon Lake trailhead outside Aspen, then circles through the Maroon Bells–Snowmass Wilderness, a 181,535-acre expanse dedicated by the federal government in 1980 to protect its high peaks, fragile tundra, and glacial valleys. The Four Pass Loop takes it all in, winding through flower-filled basins, skirting turquoise lakes, and topping out on four alpine passes—Buckskin (12,462 ft), Trail Rider (12,420 ft), Frigid Air (12,408 ft), and West Maroon (12,500 ft).

Most people take three to five days to complete the 28-mile route, spending nights hunkered down next to alpine lakes and streams and the days hiking between passes. Permits are required for backpacking, which helps limit crowding and protect the fragile landscape. Day trippers like us don’t need a permit—just an early alarm, some good legs, and a parking reservation or shuttle bus ticket to reach the trailhead.

Attempting the Four Pass Loop in a single day is a challenge that has caught on among trail runners and endurance hikers. Fastest Known Times are set by pros who can knock it out in under five hours. For most fit mortals, it’s a tough but doable daylong push. Our group of four’s moving time of eight hours belied how much time we actually spent snacking, ogling the views, and stopping to photograph the wildflowers.

The Four Pass Loop: Pass by Pass

For those unfamiliar with the area, part of the beauty of the Four Pass Loop is how much crowd-sourced information exists about it. Is it better to take it clockwise or counterclockwise? Do you need a bear canister (spoiler: not for a day trip)? Is there still snow lingering on the passes? Chances are, someone has asked, and answered, in the Four Pass Loop Facebook group, which now has more than 14,000 members.

For our late-July attempt, our crew chose the more popular counterclockwise direction, opting to get the steeper Buckskin Pass out of the way first. For those coming from sea level, a clockwise approach—which means a more gradual first day on the approach to West Maroon Pass—might feel more manageable. Either way, you finish at the same place you started, just above Crater Lake, before dropping back into the amphitheater of the Maroon Bells. Read on for a pass-by-pass breakdown that will give you a general sense of how long and how high each trek is actually going to take.

Buckskin Pass

Start point: About 4 miles from the Maroon Lake trailhead
Total distance: About 2 miles
Elevation gain (from trailhead): About 3,000 feet
Summit elevation: 12,462 ft
What to know: A steep, lung-busting opener with a long runnable descent to the Snowmass Lake overlook.

First pass, full hearts, can’t lose.

Buoyed by caffeine, hope, and that pink-orange sunrise, the first miles passed almost effortlessly. We fast-hiked through the aspens, leaving Crater Lake behind and settling into the rhythm of a very long day. At the base of Buckskin, we paused to shed layers and snap photos of sunflowers shimmying in the breeze. At this point, the trail started to arc upward, and the top of the pass was visible above a faint series of switchbacks scratched into the maroon-tinted hillside. The higher we went, the quieter our chatter became until we crested the saddle, the Elk Mountains stretching out like a promise of what was still to come.

Trail Rider Pass

Start point: About 5 miles from Buckskin
Total distance: About 2.5 miles (from the Snowmass Lake overlook)
Elevation gain: About 2,000 ft of gain
Summit elevation: 12,420 ft
What to know: The longest and most sustained climb of the loop.

At the Snowmass Lake overlook we slowed, gossiping about work and relationships, trying to keep the big climb at bay. Spirits were still high here, maybe lifted by all the runnable miles between Buckskin and this point. I could feel the buzz in my legs as much as in my chest — this was the good part, the part where you forget you’ve been moving for hours and still have many more to go. Running slowed to fast-hiking for most of the long, gradual ascent to Trail Rider. The broad sloping shoulder below the pass meant that the traverses between switchbacks were long and mentally-taxing. As I crested the top of the pass, I could see my friends below, each one a fleck of white t-shirt trundling along the trail. None of them knew it yet, but the views awaiting were some of the best we’d see all day: a sweeping panorama of the rugged Elk Mountains to the southwest, including the hulking Treasure Mountain massif.

Frigid Air Pass

Start point: About 7.5 miles from Trail Rider
Total distance: About 2 miles
Elevation gain: 1,200 feet
Summit elevation: 12,415 ft
What to know: A steep climb that opens into Fravert Basin with its sheer cliffs, green meadows, and big sky.

The stretch to Frigid Air was long, a rhythm-finding sort of section where we each moved at our own pace without needing to talk. Late-summer fireweed lit up the trail, and at a shady creekside campsite we finally dug into the cookie bars we’d each been hoarding. I ran most of this section, until the trail started climbing through an expansive alpine meadow and made moving fast difficult. We all regrouped in a clutch of yellow, purple, and pink wildflowers along a near-dry creekbed and ate our chicken salad wraps before starting the true ascent. From there, it was a steep but short march to the top, on more zig-zaggy switchbacks etched into the hillside. Once we topped out, we found a sky with two stories to tell: bright blue in one direction, storm clouds in the other. Fravert Basin, one of the prettiest places in the Elk Mountains, still draped in mid-summer green and dotted with crystalline lakes, sprawled out indifferently below.

West Maroon Pass

Start point: About 2.5 miles from Frigid Air
Total distance: 1 mile
Elevation gain: 850 feet (easy!)
Summit elevation: 12,490 ft
What to know: Famous for wildflower meadows in summer and is a passage between Aspen and Crested Butte.

We jogged down from Trail Rider with a new purpose: outrun the storm. Runnable terrain and a carpet of pink paintbrush and purple larkspur abetted our mission. The trail undulated gently, and the short distance between the final two passes bolstered our confidence — and legs. By the time West Maroon came into sight, we knew the game: get up and over before the sky opened. This was our quickest summit, and we arrived one by one and fired off a satellite text to our shuttle driver — two and a half hours to make it back. Ambitious, I thought, but we committed. The rain came in sheets as we each settled into our own pace. I bribed myself with the dregs of my candy salad—one gummy grapefruit here, a chunk of licorice there. I knew this would be the most challenging part of the day: the West Maroon Trail is rocky, uneven, technical, and frustrating. If there was ever a time to lock in, it was now.

That morning, I’d stopped to watch the sunrise paint the Bells pink. Thirteen hours later, soaked and shivering beneath those same peaks, I felt newly in awe—of us and our journey through them.

What to Pack for the Four-Pass Loop

Whether you’re tackling the loop in a single day or savoring it over several, packing smart can make the difference between a joyful outing and a sufferfest. Here’s what I carried—and what I’d recommend for anyone heading out for a day.

Backpack: For my single-day Four Pass Loop attempt, I used the Salomon Adv Skin 12 running vest. With a 12 liter volume and featherweight build (247 grams), it had more than enough room for food, layers, and safety gear. The pack comes with 500ml soft flasks and can also accommodate a hydration bladder. To save weight—and because of the abundance of water along the route—I skipped the bladder and carried a Katadyn BeFree 1 liter water filter instead. Tempting as it is to sip straight from alpine streams, always filter here; the Four Pass Loop is a high-traffic zone.

Trekking poles: While much of the loop is runnable, the steep ascents and descents will wear on your legs (and mind). Poles help enormously. I swear by my Black Diamond Carbon Zs: light, durable, and packable enough to forget about when they’re stashed. Any collapsible model will do, but bring something you trust.

Footwear: Comfortable, familiar shoes are non-negotiable—one blister can ruin your day. For some, that means well-broken-in hiking boots; for others, trail runners. I wore the La Sportiva Prodigio Pro, a cushioned but grippy trail shoe that kept me steady on both loose scree and firm trail. Whatever you choose, don’t debut them on the loop!

Headwear: Colorado sunshine is relentless. A brimmed hat or bucket hat and full-coverage sunglasses are essential. I am devoted to the Skida brim hat and Oakley Sutro Lite sunglasses.

Rain gear: Summer in the Elk Range means afternoon storms, even on “bluebird” forecast days. At minimum, bring a lightweight shell like the Patagonia Houdini; better yet, a full rain jacket. I carried Gorewear’s Concurve GORE-TEX jacket, which proved its worth during the soaking eight-mile shower we endured back to the trailhead. A good hood is underrated — mine fit snugly over a hat, keeping water out of my eyes and warmth in.

Layers: Even if you’re moving fast, temps swing wildly above treeline. A long-sleeve sunshirt or thin baselayer is smart insurance. I started and ended the day in my Outdoor Research Echo hoody, even though I ran most of the loop in a tank top. I debated throwing a pair of rain pants in my pack; if you’re doing the loop in late summer or early fall, this is definitely a smart addition as would be a thin insulated layer.

Snacks: Fuel is personal, but as with shoes, don’t gamble with untested foods on game day. I like to mix “sports food” with “real food” to keep morale high. For the Four Pass Loop, I carried chews and gels from GU Energy, Skratch bars, Larabars as my “sports food,” plus a chicken salad wrap, homemade cookies, pretzels, and a bag of candy salad (assorted gummies from Whole Foods). My friends and I saved the real food for scenic pauses and relied on the quick sugar hits when energy flagged.

Optional but highly recommended: A headlamp (you may finish in the dark), extra socks (for creek crossings), Buff/neck gaiter, lightweight gloves, first-aid kit, and a GPS communicator like the Garmin inReach.