One of Colorado's premier backpacking routes circling through four high mountain passes (Buckskin Pass, Trail Rider Pass, Frigid Air Pass, and West Maroon Pass) with spectacular wilderness scenery throughout.
The Four Pass Loop is one of Colorado's premier multi-day backpacking routes, circumnavigating the Elk Mountain Range through the Maroon Bells-Snowmass Wilderness near Aspen and crossing four high mountain passes, all above 3,660 m (12,000 ft). The standard trailhead is at Maroon Lake, reached via the mandatory Aspen Highlands shuttle during summer operating hours from late June through early October; a Maroon Bells-Snowmass Wilderness overnight permit is required for all camping and must be reserved through recreation.gov. Camping is only permitted at designated sites along the loop. The 80 km (50-mile) circuit is typically completed in three to five days, crossing Buckskin Pass (4,117 m / 13,500 ft), Trail Rider Pass (3,963 m / 13,000 ft), Frigid Air Pass (3,932 m / 12,900 ft), and West Maroon Pass (3,904 m / 12,800 ft) in the standard clockwise direction. Total elevation gain exceeds 2,700 m (8,858 ft) across the full loop. Terrain varies from forested valley floors with willow-lined creek crossings to open alpine meadows blanketed with wildflowers and fully exposed rocky ridgelines above treeline. All four passes sit above treeline and are completely exposed to alpine weather; afternoon thunderstorms are the primary hazard from July through mid-August. Surface conditions range from packed dirt and boardwalk sections in the valley floors to loose scree and rocky terrain on the upper pass approaches. Water is abundant from creek crossings throughout the route and must be filtered or chemically treated. Bear canisters are required in the Maroon Bells-Snowmass Wilderness and ranger-issued fines apply for non-compliance. No huts or facilities exist along the loop; hikers must carry all camping equipment and full food supplies for the planned duration. Navigation is straightforward in clear conditions but a topographic map and GPS are advisable for poor-visibility travel near the passes.
Trail facts
- Trail area
- Maroon Bells-Snowmass Wilderness, Aspen
- Best season
- Mid-July to mid-September
Highlights
- Four high passes above 12,000 feet
- Alpine lakes and wildflower meadows
- Remote wilderness solitude
- Spectacular Elk Mountains scenery
Tips for visiting
- Book Maroon Bells-Snowmass Wilderness overnight permits at recreation.gov as soon as the reservation window opens (typically in February); the loop is extremely popular and permits sell out within hours.
- Bear canisters are mandatory in this wilderness area; plan food storage carefully as canister space limits what can be carried for a five-day trip.
- Plan each day to cross high passes before noon to minimize exposure to afternoon lightning; adjust camp placement the night before to allow early morning summit starts.
- A water filter or purification tablets are essential; the loop has abundant water sources throughout but giardia is present in most backcountry water in this region.
- Trekking poles and microspikes for early-season snow significantly reduce fatigue and improve safety over 80 km with 2,700 m of cumulative gain.
- The clockwise direction (crossing Buckskin Pass first) is generally preferred as the Buckskin approach is better defined and the descent off West Maroon Pass is more gradual.
When to visit
Mid-July to mid-September is the optimal window when all four passes are reliably snow-free and wildflowers are at peak bloom. September sees noticeably fewer crowds and spectacular golden aspen color in the valley sections.
Accessibility
The Four Pass Loop is not suitable for visitors with mobility limitations. The route involves 80 km of mountain terrain with four high alpine passes above 3,900 m, steep rocky ascents and descents, multiple creek crossings, and multi-day camping with no support infrastructure along the route.
Frequently asked questions
Is a permit required for the Four Pass Loop?
Yes. Overnight camping in the Maroon Bells-Snowmass Wilderness requires a reservation-based permit available through recreation.gov. Day hikers crossing the passes do not require a camping permit but must use the Maroon Bells shuttle during operating hours.
How experienced do hikers need to be for the Four Pass Loop?
The loop is demanding and requires multi-day backpacking experience, comfort at elevations above 3,600 m, and the ability to navigate above treeline in changeable weather. Day hiking experience alone is insufficient preparation for this route.
When are the passes reliably snow-free?
Most years the passes are snow-free from mid-July through mid-September. Significant snowfields can remain before and after these dates; an ice axe and microspikes may be advisable for early-season crossings of Frigid Air and Trail Rider passes.
What wildlife might be encountered on the loop?
Black bears are present throughout the wilderness and bear canisters are mandatory. Elk, mule deer, marmots, and pikas are commonly seen. Mountain goats and bighorn sheep occasionally appear on the high passes above 3,800 m.