Mount Sanitas Trail

Mount Sanitas is Boulder's hill, the 6,863-foot ridge at the west end of Mapleton Avenue that the town climbs before work, after work, and on lunch breaks, with the city below the whole way. The loop goes up the Mount Sanitas trail on the steep west ridge and down the East Ridge trail to the Sanitas Valley, 3.1 miles with 1,400 feet of gain, and it is the most crowded trail in the county at 7 AM.

From the Centennial trailhead on Sunshine Canyon Drive, the Mount Sanitas trail climbs the west ridge at once: rock steps, sandstone slabs, and a few short scrambles up a ridge that is open to the sun and the view, with Boulder spread out to the east and the Flatirons to the south. The grade rarely eases in the 1.3 miles to the summit, a rocky point with a bench.

From the summit, the East Ridge trail drops steeply down the ridge's east side on rock and steps to the Sanitas Valley trail, a wide gravel road that runs south down the valley between the two ridges back to the trailhead. The Dakota Ridge trail on the valley's east side is the gentler alternative for either half.

The Centennial trailhead is on Sunshine Canyon Drive just west of the Mapleton Avenue and 4th Street junction, a small lot that is full by 6 AM most days; the Mapleton lot a block east and the streets nearby are residential permit zones enforced by the city. Walking or biking from town is the normal way in. No fee or permit. Toilets at the trailhead.

Dogs are allowed on leash, or off leash with a Boulder voice-and-sight tag where the trailside signs permit it. The city began a multi-year repair of the Mount Sanitas and East Ridge trails in 2026, rebuilding stone steps about 1,000 feet below the summit and closing social trails; no full closures are planned, but expect brief detours around work crews into 2027. The scrambles and the crowds are why the loop is not marked kid-friendly; the Sanitas Valley trail on its own is a fine family walk. Carry water; there is none on the ridge. Trail runners use the loop as a race course and pass often. Boulder is at the trailhead. The Boulder hikes page has the Chautauqua trails across town.