Thornton Lakes and Trappers Peak
North CascadesBest Jul–Oct
Alpine lakes and a scramble summit deep in the North Cascades backcountry.
About This Trail
Thornton Lakes trail cuts into the heart of the North Cascades, delivering alpine lakes and a scramble peak in under 10 miles. The first two miles follow an old logging road through second-growth forest with gentle grades. After that, the trail steepens through dense forest on rooty switchbacks that demand careful footwork, climbing steadily to a signed junction inside North Cascades National Park at mile 4.2.
From the junction, hikers choose between descending 600 feet on a steep, often muddy path to the lowest Thornton Lake, or climbing nearly 1,000 feet in under a mile to the summit of Trappers Peak. The peak scramble uses hands in places but stays low on the exposure scale. From the top, the Pickets Range and Mount Triumph dominate the skyline, with the Skagit River valley and Newhalem far below. The three Thornton Lakes sit in a glacially carved basin with an austere, alpine character that rewards the long approach.
Backpackers need a National Park backcountry permit for overnight stays at the lakes. Day hikers need only a Northwest Forest Pass for the trailhead. The access road is steep, narrow gravel but manageable for most cars. Plan 7 to 9 hours for the full out-and-back including Trappers Peak.
Forecast
Astronomy
Trail Conditions
“The road was passable with my sedan, although I had to crawl along at 5mph for the last few miles - high clearance would have been better.”
Last report: Jul 12, 2026
Scorecard
Safety & Considerations
Today's Hazard
- Strong sun — sunscreen, hat, and sunglasses recommended; water reflection adds glare near the lake
Persistent Hazards
- Steep, rooty trail sections with slippery footing when wet
- Steep muddy descent to lake basin
- Scramble sections on Trappers Peak requiring hand use
- Late-season snow on upper route into October
- Rough gravel access road
Getting There
Small trailhead lot with vault toilet. Northwest Forest Pass required. The 5-mile Thornton Lakes Road is steep gravel with brake bumps but passable for standard passenger cars in dry conditions. Gets rougher when wet.
From Marblemount, drive Highway 20 east 11 miles. Turn left onto Thornton Lakes Road between mileposts 117 and 118. Follow the rough gravel road 5 miles to the trailhead. The first 2 miles of trail are nearly flat on an old road bed before the real climbing begins on forest switchbacks.
Start by 8 AM to allow enough time for both the lakes and Trappers Peak. The trail sees moderate traffic on summer weekends but stays quiet on weekdays. Late starts may not leave enough daylight for the full Trappers Peak extension.
Recent Reports
Beautiful 3 days/2 nights. Road to trailhead was steep in places but most could get there if go slow but higher clearance better.
The road was passable with my sedan, although I had to crawl along at 5mph for the last few miles - high clearance would have been better. Trail conditions were fine, a little mud in places and a bit of snow pack at the summit.
Mellow groomed trail for first 2 miles then gets more challenging, going from frequent staircases of root and rock (some quite steep) to the scramble and condensed ascent toward the end after the trail fork between the lakes and the peak. Some muddy sections but no snow on the trail except maybe 10 steps toward the end.
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