West Boulder · The Flatirons

Green Mountain

Green Mountain is a Flatirons summit on Boulder's skyline, about 8,144 feet high, reached by a hard 5.5-mile round-trip climb from Gregory Canyon or a short, moderate 2.6-mile route along the West Ridge, with a bronze peak-finder and big Continental Divide views at the top.

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Green Mountain quick facts

Distance: Depends on the route. The classic Gregory Canyon to Ranger to E.M. Greenman climb is about 5.5 miles round trip. The West Ridge from Flagstaff Road is the short way at about 2.6 miles round trip, and the steep Saddle Rock line runs about 4.6 miles.
Elevation gain: About 2,300 feet from Gregory Canyon or Saddle Rock. The West Ridge gains only about 600 feet.
Summit elevation: About 8,144 feet. (The current NAVD88 survey lists the summit at 8,148 feet.)
Difficulty: Hard from Gregory Canyon or Saddle Rock, a steady climb of roughly 2,300 feet. The West Ridge is moderate and much easier.
Dogs: On the approach trails, dogs need a hand-held leash or a City of Boulder Voice and Sight tag. Dogs are not permitted on the upper E.M. Greenman section that leads to the summit, so check the OSMP dog map before you go.
Fee / parking: The park is free to hike. Gregory Canyon is a fee trailhead: a $5 daily OSMP parking permit or a $25 annual permit, paid at the station or through ParkMobile. It has 37 spaces and fills early. The West Ridge trailhead on Flagstaff Road has free roadside parking.
Trailheads: Gregory Canyon at the base of Flagstaff Road for the classic climb; Chautauqua Park, connecting via the Bluebell-Baird and Gregory Canyon trails; and the Green Mountain West Ridge trailhead about 5 miles up Flagstaff Road for the short way.
Best season: Late spring through fall for a dry summit. In winter the Gregory Canyon access road can close with ice and snow and the upper trail ices up, so bring traction.

Green Mountain at a glance

Green Mountain is one of the five summits that make up Boulder's mountain backdrop, sitting between Flagstaff and Bear Peak, above the tilted slabs of the Flatirons. It's a local favorite: high enough to feel like a real summit, close enough that you can climb it before lunch, and laced with enough trails that you can pick your effort level. It's managed by the City of Boulder's Open Space and Mountain Parks, so it's free to hike, with the usual OSMP dog and parking rules.

Routes to the summit

There are three classic ways up, all sharing the same reward. The Gregory Canyon approach is the standard: about 5.5 miles round trip and roughly 2,300 feet of gain, up Gregory Canyon Trail to Ranger Trail, past the historic Green Mountain Lodge, and finally a short push up E.M. Greenman to the top. The Saddle Rock line starts at the same trailhead but goes straight up: shorter at about 4.6 miles, and much steeper, with a ladder from the 2013 flood repairs along the way. The West Ridge is the easy back door, about 2.6 miles round trip and only about 600 feet of climbing, starting high on Flagstaff Road.

Distance, elevation, and difficulty

From Gregory Canyon or Saddle Rock, treat Green Mountain as a hard hike. The climb is steady and rocky, and at altitude the last stretch of E.M. Greenman feels every bit of its grade, which is exactly why Boulder hikers use it to train for higher peaks. The West Ridge is the exception: mostly rolling forest and meadow with one steeper final section, so it's a good pick if you want the summit without the full grind. The summit itself sits at about 8,144 feet (the current NAVD88 survey lists it at 8,148).

The summit and the peak-finder

The top is a jumble of granite boulders that you scramble up for the last few feet. Set into the rock is a bronze peak-finder, a marker that names the mountains laid out around you: the plains stretching east, and the high line of the Indian Peaks and the Continental Divide to the west. It's a genuine 360-degree view and one of the best in town, which is a big part of why this is such a popular climb.

Parking and fees

Hiking Green Mountain is free; parking is where the fee comes in. Gregory Canyon is an OSMP fee trailhead at the base of Flagstaff Road, so you'll need a $5 daily parking permit or a $25 annual OSMP permit, paid at the self-service station or in advance through ParkMobile. There are only 37 spaces and they go fast on nice days, so come early. The trailhead is open 5 a.m. to 9 p.m., and the access road can close in winter when it's icy. If you start from the West Ridge trailhead higher up Flagstaff Road, parking is free along the roadside instead.

Dogs on Green Mountain

Dogs are welcome on the approach trails, either on a hand-held leash or under Voice and Sight control with a valid City of Boulder tag. The catch is the summit: dogs are not permitted on the upper E.M. Greenman section that leads to the top. If you're hiking with a dog, plan a turnaround or a different trail, and check the OSMP dog regulations map before you head out.

Best season and what to bring

Late spring through fall is prime, with a dry trail and a clear summit. Summer afternoons bring thunderstorms to the Front Range, so start early and be off the top by early afternoon. In winter the Gregory Canyon access road can close with ice and snow, and the upper switchbacks hold snow, so bring traction and check conditions. Whatever the season, carry more water than you think you need for the climb.

Nearby trails and guides

All hikes in Boulder: the full hiking hub, sorted by difficulty.
Chautauqua Park: the trailhead hub at the foot of the Flatirons, and a way onto Green Mountain from the north.
Royal Arch Trail: a shorter, steep Chautauqua classic if the full summit is too much for the day.
Mount Sanitas: a lower, quicker foothill summit on the north side of town.

Recommended nearby

A few local spots we'd point a Green Mountain day toward.

Gear / rental

[CLIENT SLOT: featured outdoor shop near Green Mountain]

[One honest line: traction, layers, or trail gear for the summit push.]

Cafe

[CLIENT SLOT: featured cafe near Chautauqua / Gregory Canyon]

[One honest line: coffee or a bite before or after the climb.]

Guide / shuttle

[CLIENT SLOT: featured guide or shuttle near Boulder]

[One honest line: a guided hike or a ride to the trailhead.]

Green Mountain FAQ

How long is the hike to the summit of Green Mountain?

It depends on your route. The classic Gregory Canyon approach (Gregory Canyon to Ranger to E.M. Greenman) is about 5.5 miles round trip with roughly 2,300 feet of gain. The Saddle Rock approach is shorter but steeper at about 4.6 miles. The West Ridge from Flagstaff Road is the short, gentle way in at about 2.6 miles round trip and only about 600 feet of climbing.

How hard is Green Mountain?

From Gregory Canyon or Saddle Rock it's a hard hike, a steady 2,300-foot climb over rocky, steep trail, and a good training route for higher peaks. The West Ridge is the exception: it rolls along near the top of Flagstaff Road and only pitches up for the last stretch, so it's moderate rather than hard.

Is there a fee to hike Green Mountain?

Hiking the mountain is free. The cost is parking. Gregory Canyon is an OSMP fee trailhead, so you need a $5 daily parking permit or a $25 annual OSMP permit, bought at the self-service station or through ParkMobile. If you start from the West Ridge trailhead higher on Flagstaff Road, there's free roadside parking instead.

Can you bring dogs on Green Mountain?

On the approach trails, yes, on a hand-held leash or under Voice and Sight control with a City of Boulder tag. But dogs are not permitted on the upper E.M. Greenman section leading to the summit, so you can't take a dog all the way to the top that way. Check the OSMP dog regulations map before you go.

What's at the summit of Green Mountain?

The top is capped by large granite boulders you scramble up to a summit marker: a bronze peak-finder disk set in the rock that names the peaks around you, from the plains east to the Indian Peaks and the Continental Divide west. The 360-degree view is one of the best in Boulder.

Sources

Facts on this page are drawn from these sources: