Thornton Lake Trail
in Washington · centroid 86 mi from Seattle
This trail provides views of high mountain lakes and nearby peaks. The trail is level - and often brushy - for the first 2 miles (3.2 km) then gains elevation through cool, old-growth forest. Stop on the ridge above Thornton Lake (4.5 miles/7.2 km) for great views.
For a longer, more strenuous day, scramble up Trapper Peak or down to the lake. Difficulty: Moderately strenuous. Distance and elevation: 10.4 miles (16.7 km) roundtrip with 2,300 ft (700 m) elevation gain.
Access: From milepost 117 on State Route 20, follow the Thornton Lake Road for 5 miles (8 km) to the trailhead (rough road - not recommended for low-clearance vehicles). Leashed dogs allowed up to the national park boundary. Backcountry camping is allowed in designated sites only with a backcountry permit.
- States
- Washington
- Trail type
- National Park trail
- Centroid nearest city
- Seattle, WA · 86 mi · ~2.5 hr drive
- Centroid coords
- 48.6546°, -121.3259°
About North Cascades National Park
This trail is inside North Cascades National Park, a national park managed by the U.S. National Park Service. Conditions, road status, trail closures, and reservation requirements are published on the park's NPS page — check it before driving in, especially in winter or during major weather events.
Official NPS trail page: https://www.nps.gov/places/thornton-lake-trail.htm
Park homepage: https://www.nps.gov/noca/index.htm
Plan your hike
Maps + permits: long-distance trails like this often require permits for through-hiking, backcountry camping, or specific sections (especially in National Parks). Check with the maintaining organisation listed above and the relevant land manager before booking travel.
Water + supplies: water sources vary seasonally on most U.S. trails. Carry a filter and consult current trail-condition reports — through-hiker journals (PCT-L, AT Reddit, etc.) and the maintaining organisation publish regular updates.
When to go: hiking seasons vary widely with elevation, latitude, and snowpack. Through-hikers traditionally start the AT in March-April (Springer northbound) and the PCT in late April (Campo northbound). High-elevation western trails (CDT, JMT, Wonderland) generally aren't passable until July.
If you've hiked Thornton Lake Trail and have current notes (water sources, trail closures, permit changes), tell us at /contact — we update pages as we learn.
Stay nearby
Other trails within 50 miles
River Loop Trail
3 miles from this trail's centroid
Diablo Lake Trail
10 miles from this trail's centroid
Fourth of July Pass Trail
11 miles from this trail's centroid
The Great North Cascades Traverse
16 miles from this trail's centroid
Happy Panther Trail
16 miles from this trail's centroid
Fisher-Thunder-Park-Cascade Cross-Park Trek
17 miles from this trail's centroid
Sources
Trail data on this page is compiled from OpenStreetMap contributors (ODbL), the maintaining organisation's public-facing materials, and Wikipedia (CC BY-SA where excerpts are quoted). Distance, terminus, and descriptive text for nationally-designated trails are hand-curated from federal land-manager websites and trail-association sources. We do not modify the underlying data; this page presents what is already publicly recorded. To suggest corrections, see our methodology page.