TrailAspen Ridge – Boulder Ridge
Boulder scramble through aspens to Phelps Lake. 6.2mi, 1,140ft gain. Moderate grit required.

A tactical Snake River canyon push through rugged terrain. This 5-mile roundtrip follows the northern stretch of the Snake River through Flagg Canyon with 340 feet of elevation gain. Expect a narrow, rocky dirt trail with ups and downs, fallen trees, canyon edges, and river access. Packed with wildland grit—not a tourist stroll. Spring through fall only.
Easy to Moderate
Snake River follows the canyon throughout the hike, offering river access and views of the parkway landscape. Mountain views frame the scenic corridor.
• The trail crosses the parkway—watch for vehicles and stay alert • The false summit at mile 2 will tempt you to turn back; the best canyon views come after mile 2.5 • The northeast side of Polecat Creek Loop Trail access point is the official trailhead; don't start from elsewhere • Early morning (6-7am) secures quiet river access and cooler hiking • The descent is steep in sections; trekking poles are worth their weight
Spring, Summer, Fall
Safe for older kids (8+) with strong legs and no fear of heights. Canyon edges require hand-holding for young children. The parkway crossing demands adult supervision. Not ideal for toddlers or those with mobility issues.
Hikers report a solid, gritty Snake River experience with real terrain challenges. Most say the 340-foot elevation gain is doable but leaves your legs knowing they worked. The canyon views justify the effort; river access is a major draw. Crowded summer weekends can diminish the wildland vibe, but weekday mornings deliver solitude.
No permits required for day hike
No shuttle required; self-parking at Flagg Ranch
Canyon edges drop toward river with no guard rails. River crossing presents slip hazard and drowning risk if unexpected flood flow occurs. Fallen trees and rocky outcrops create tripping hazards. Narrow trail crosses the John D. Rockefeller, Jr. Memorial Parkway—watch for vehicles. Sun exposure on open ridges can cause heat exhaustion.
5-mile roundtrip with 340 feet elevation gain and 5% average slope. Narrow dirt trail with numerous ups and downs. Obstacles include fallen trees, canyon edges without guardrails, and rocky outcrops. Not wheelchair accessible. Requires hiking boots and balance.
Safe for older kids (8+) with strong legs and no fear of heights. Canyon edges require hand-holding for young children. The parkway crossing demands adult supervision. Not ideal for toddlers or those with mobility issues.
Flagg Ranch Information Station at trailhead; nearest full amenities at Colter Bay (15 miles south)
Hikers report a solid, gritty Snake River experience with real terrain challenges. Most say the 340-foot elevation gain is doable but leaves your legs knowing they worked. The canyon views justify the effort; river access is a major draw. Crowded summer weekends can diminish the wildland vibe, but weekday mornings deliver solitude.
" Hikers report a solid, gritty Snake River experience with real terrain challenges. Most say the 340-foot elevation gain is doable but leaves your legs knowing they worked. The canyon views justify the effort; river access is a major draw. Crowded summer weekends can diminish the wildland vibe, but weekday mornings deliver solitude."
Labeled 'easy' by NPS but don't be fooled. 340 feet of elevation gain plus rocky obstacles and canyon edges make it moderate in grit. Doable for fit hikers; brutal for beginners. Be honest about your fitness before committing.
Yes. No guardrails, 100+ foot drops to river in places. Hand-hold small children. Don't take selfies at the edge. Rock scrambles near drops demand focus and balance.
Solo hiking is doable on this trail, but cell service is unreliable. Tell someone your plan. A partner is safer given the canyon exposure. Bears are present; make noise.
Carry 2L minimum. The Snake River is nearby but water quality is uncertain without filtering or treatment. Bring a lightweight filter if you want to refill at the river. Summer heat and sun exposure increase sweat loss.
Winter (Nov-April)—snow and ice make it impassable. Muddy spring (April-May) is slippery near river. Peak summer crowds (July-August) degrade solitude. Fall (Sept-Oct) is ideal.
Yes. The trail crosses the John D. Rockefeller Jr. Memorial Parkway. Stay alert for vehicles. Look both ways. Don't space out on the crossing.
Strongly recommended. The rocky terrain and steep descent are tough on knees. Poles give stability on uneven ground and reduce injury risk. Most experienced hikers carry them on this trail.
6 listings
4 listings
Information is compiled from official sources, verified traveler reviews, and editorial research. Learn how YourNPGuide works →
We use basic, essential analytics to measure traffic. You can also allow deeper first-party analytics that help us improve our park guides. We never sell your data. Learn more
We use basic, essential analytics to measure traffic, plus optional deeper analytics to improve our park guides. We never sell your data. Choose what you allow. Learn more
Essential analytics that measure basic traffic stay on. The deeper, first-party analytics below are optional — turn on what you are comfortable with. We never sell your data. Read the notice
Site function plus basic visit counts via Google Analytics and Search Console — needed to see how many people visit. Always on.
How far you scroll, whether you finish an article, and which sections are read — so we know which guides to improve.
Clicks on links and buttons, and searches you run on the site — so we can fix confusing navigation and content gaps.