green pine trees on brown rocky mountain under blue sky during daytime

Devil’s Thumb is a prominent spire visible from almost anywhere in Boulder along the Flatirons skyline. It’s located just south of Bear Peak and has a distinct thumb-shaped shape. Every climber in Boulder has probably considered climbing it at some point, and apparently non-climbers did as well: a steel ladder was once installed to make the summit more accessible, but it has since been removed. The only remnant of the ladder is a steel pole on the summit’s east side, but it serves as an excellent rappel point for those willing to brave a laborious approach to the Thumb. There is also a two-bolt anchor with chains on top. The western side of Devil’s Thumb has an incredible, towering overhang, while the eastern side has its own 20-foot overhang, making the summit a technical climb regardless of how you approach it. There are two moderate routes up the east face’s weaknesses, a 5.10d route up the southwest side, an aid route on the northwest side, and what appears to be a very fun line of bolts on the north face.

The South Mesa Trailhead is where you should start your ascent. toward the Matron and Shadow Canyon, take the Mesa trail to the west. Follow the Shadow Canyon trail to the NW up into the canyon from the Mesa/Shadow Canyon junction. You start to see Devil’s Thumb in the distance to the east (to the right).

The northwest side of Devil’s Thumb is your destination (at least for moderate routes) once you start to notice a sizable boulder/talus field on your right; detour from the trail at any time and rock-hop your way there. If you’re unaccustomed to it, class 4 scrambling can be frightening, but the sections are brief and you’re already very close to the base of Devil’s Thumb at this point. The hopping gradually transforms into steep hiking on loose rock. When you arrive, make your way around the northern side before climbing up and over a boulder to access the east face.

Here are some tips and precautions to keep in mind when engaging in these activities:


  1. Stay on designated trails to avoid disturbing fragile ecosystems and minimize your impact on the environment.
  2. Bring plenty of water, snacks, and sun protection, as the altitude and dry climate can be dehydrating and sunburns can occur quickly.
  3. Check weather conditions before starting your hike and be prepared for sudden changes in weather.
  4. Wear sturdy and comfortable shoes with good traction to prevent slips and falls.
  5. Tell someone where you are going and when you expect to return, and consider bringing a map or GPS device.

Rock Climbing:

  1. Always climb with a partner and use proper safety equipment, such as ropes, helmets, and harnesses.
  2. Check the condition of the rock and the equipment before climbing to ensure everything is in good working order.
  3. Start with easier climbs and gradually work your way up to more difficult routes as you gain experience.
  4. Be aware of potential hazards such as loose rock, falling debris, and unexpected weather changes.
  5. Respect the environment by not damaging the rock or disturbing wildlife.

In general, it is important to be aware of your surroundings and take precautions to stay safe while hiking and rock climbing in Boulder, Colorado.