From the trailhead cross the footbridge and take the Devil's Thumb Trail #902, which climbs steeply for about 0.5-miles on an old road. The shorter Devils Thumb Bypass turns right (north) in 0.8 miles, just before the second bridge and crosses open meadows to the north. In 1.5 miles, the Diamond Lake Trail
#975 forks right to the north (#975 leads past Diamond Lake
to connect to the Arapaho Pass Trail
From the Diamond Lake Trail
junction, it is another 0.6 miles to Jasper Lake, a very popular camping area with limited designated sites. The trail continues for a mile to Devil's Thumb Lake. Several switchbacks lead up the steep side of a ridge to reach the Continental Divide. Snow and ice can be a problem until late July.
From the top, it is 0.6 miles to the north to Devil's Thumb Pass and three miles to the King Lake Trail
#901. It is not difficult to see the High Lonesome Trail
below and west of the Devil's Thumb Trail. Finding the Devil's Thumb Trail from the High Lonesome Trail