ElevationAscent: 3,067' 935 m
Descent: -3,067' -935 m
High: 5,018' 1,530 m
Low: 2,499' 762 m
GradeAvg Grade: 12% (7°)
Max Grade: 58% (30°)
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“A pleasant, steep trail through dense forest to subalpine lakes in a beautiful mountain basin.”— Sarah Baker
The first two miles of trail gently ascend an old road grade through new growth forest. Then, the trail trail climbs steadily upwards through mature hemlock forest until it reaches meadows and attains the ridge. The ridge offers spectacular views of Triumph Peak and lower Thornton Lake.
The short, steep trail down to lower Thornton Lake is often muddy and slippery. Be especially careful on the rock and floating-log scramble to cross the outlet of the lake and reach the camp.
Thornton Lake has three sites which are popular and fill quickly during busy periods. Camping is not allowed on the ridge above the Thornton Lakes, Trappers Peak, or at the second Thornton Lake. Climbers attempting Triumph Peak may obtain a permit to camp at the Triumph Col cross-country zone.
At the third switchback, the trail steepens and continues to climb up many moderate to steep switchbacks. The trail ascends through forested slopes, through a wet meadow and over a creek before officially entering North Cascades National Park. At 4.5 miles, the trees thin, and the trail breaks out into meadows of heather and huckleberry and continues to climb to an open ridge. From the ridge, you get expansive views of Mt. Triumph, Teebone Ridge, and the Skagit Valley.
A scramble route leaves the main trail at the ridge and ascends steeply towards Trappers Peak. If you spend the night at Thornton Lakes, this can be a great extension of your trip. The views from Trappers Peak of the three Thornton Lakes and the rugged Picket Range are truly spectacular.
The main trail descends steeply for 0.6 miles down 500 ft along a lesser ridge with views of lower Thornton Lake and Triumph Peak beyond. Be careful crossing the lake outlet as the boulders and rocks can be wet and slippery! The maintained trail ends at lower Thornton Lake where there are 3 permit campsites and a compostable toilet.
From lower Thornton Lake there is a primitive climber's path that proceeds to the upper lakes and Triumph Col. The two lakes above are cupped in their own rocky basin, forming classic cirque lakes that were created by glaciers which carved the rock basin before retreating to where they are today.
This ecosystem has very fragile vegetation. Make sure to avoid trampling vegetation by running and resting only on durable surfaces such as the trail, snow, or rocks.
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Land Manager: NPS - North Cascades National Park