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Colorado Trails

Denver: Devils Thumb Loop

Bag two peaks on this 9-mile, fido-friendly loop around Boulder's signature Flatirons.

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Trail Facts

  • Distance: 11.0
  • Miles from city center: 29



Location: 39.9674339294434, -105.258682250977

Head S then W across an open mesa dotted with pines; Devils Thumb protrudes from the Flatirons ahead


Location: 39.960765838623, -105.26634979248

Turn L @ Y onto South Fork Shanahan Ridge Trail


Location: 39.9586181640625, -105.280220031738

Take L @ Mesa Trail and head S


Location: 39.9459495544434, -105.287033081055

Turn R and begin knee-popping, 2,000-ft. ascent into the verdant contours of Shadow Canyon


Location: 39.9565162658691, -105.297164916992

Reach saddle and take L


Location: 39.9536018371582, -105.299415588379

South Boulder Peak (8,549 ft.): Eldorado Canyon drops off precipitously to the south Continue back to saddle and turn L onto Bear Peak Saddle Trail.


Location: 39.9602661132812, -105.295166015625

Bear Peak (8,461 ft.): Scope the Great Divide on the western horizon then descend north into the shady environs of Fern Canyon and return to the Mesa Trail


Location: 39.9645843505859, -105.279815673828

Turn R back onto the Mesa Trail and hike .6 miles back to the South Fork Shanahan Ridge Trail to close loop then return to trailhead

Benchmark and the Great Divide

Location: 39.9600219726562, -105.294891357422

A USGS marker notes the 8,461-foot summit of Bear Peak, where views stretch west to the snow-capped glaciers of the Indian Peaks and the Continental Divide. ©Andrew Matranga

The Angle of the Flatirons

Location: 39.9607543945312, -105.29411315918

From above, the Flatirons are less-than-vertical, demonstrating the uplift that occured many geologic years ago. ©Andrew Matranga

View into Eldorado Canyon

Location: 39.9535827636719, -105.29940032959

Looking southwest from South Boulder Peak. ©Andrew Matranga

Close up of Devil’s Thumb

Location: 39.9519271850586, -105.290298461914

A near-vertical shot of the iconic Devil’s Thumb. ©Andrew Matranga

Down the Range

Location: 39.9482498168945, -105.290344238281

A view south from Shadow Canyon. Note double ears of “Mickey Mouse Wall” near Eldorado Mountain. ©Andrew Matranga

Like a lonesome hitchhiker

Location: 39.9521102905273, -105.289283752441

View from below in the depths of Shadow Canyon, the protruding granite spire of Devil’s Thumb pierces the Boulder Skyline like a wayward roadside straggler. ©Andrew Matranga

Flatirons Up Close

Location: 39.9649391174316, -105.289558410645

Viewed This is an unnamed Flatiron above “The Slab” and below Bear Peak. ©Andrew Matranga

Summit of Bear Peak

Location: 39.9602508544922, -105.295074462891

A stack of boulders greets the tired hiker to Bear Peak, Boulder’s second highest summit. ©Andrew Matranga

Scrambling Atop Bear Peak

Location: 39.9624099731445, -105.29443359375

The last few hundred yards to the summit follow an exposed ridgeline requiring some hand-over-hand scrambling. ©Andrew Matranga