Mule deer
Odocoileus hemionus
Year-round
DawnDusk
Photo: NPS Photo — public domain
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Boulder · Moderate
Flagstaff Mountain
The gentlest Skyline Traverse summit — drivable or hiked
Boulder Open Space & Mountain Parks
Distance4.2mi round trip
Elevation1,494ft gain
High point6,950ft summit
Typical time2.5–3.5hours
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The gentlest Skyline Traverse summit — drivable or hiked. Editorial intro forthcoming.
Trip facts
Typical duration2.5–3.5hours
Trailhead5,500ft elevation
High point6,950ft summit
Dogs: leashes required.
How you'll find it
From Boulder, take Baseline Road west to the Flagstaff/Gregory Canyon Trailhead at the base of Flagstaff Road. $5 daily parking fee for non-Boulder-County vehicles. Drive-up access to Flagstaff Summit West is open May 1–October 30.
Drive time
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We'll calculate drive time + a leave-by recommendation to beat the lot fill.
What you'll get
- 6,950ft summit reachable by foot or paved road — only Skyline peak with vehicle access
- Steep switchback trail crosses Flagstaff Road repeatedly — short but earns the elevation
- Sweeping eastern views over Boulder, the Plains, and Denver skyline on clear days
- Picnic shelters and Flagstaff Nature Center at the summit make it a half-day option
- Pairs naturally with Green Mountain via the Ranger Trail for a two-peak Skyline day
What locals know
Practical-craft notes for this specific trail — timing, route, photo, etiquette.
Trail tips
- Route
Drive-up summit + hiked summit = same place
Flagstaff Mountain's summit is accessible by both the foot trail AND a paved scenic drive. Most hikers don't realize the summit lots and the foot trail converge. The drive-up zone is open May 1 – October 30.
- Timing
Sunset programming at the summit nature center
The Flagstaff Nature Center hosts free sunset talks Friday evenings June–August. Park at the upper summit lot ($5 daily), grab a seat at the amphitheater. Combines the hike with educational programming.
- Photo
Sunrise over Boulder + plains horizon
From the eastern summit edge, you get Boulder city + plains stretching to the eastern horizon — sunrise from this 6,950ft vantage shows the curve of the earth. Worth the pre-dawn drive up.
- Etiquette
Cars + hikers share the road — watch for traffic
The foot trail crosses Flagstaff Road multiple times via switchbacks. Cyclists descending at speed and drivers focused on views combine for real collision risk. Make eye contact at every crossing.
- Gear
Microspikes Nov–Mar — paved trail ices over
The lower paved section ices over even in mild winters. Drive-up summit access closes Nov 1; the foot route stays open year-round but requires traction.
Where you'll start
Flagstaff is the rare Boulder summit you can drive to in summer — the $5 daily lot at the base of Flagstaff Road (free for Boulder County registrations) backs the trailhead, with additional paid lots scattered up the summit road May through October. No overnight stays; bring small bills for the permit machine.
Parking cost
$5 daily non-resident
Overnight
Not allowed
Boulder OSMP closes lots at sunset. Summit drive-up access closes Nov 1 – Apr 30.
Park entrance
Free
Restrooms
Vault toilets
Fills by
9am summer weekends for the base lot; summit lots fill later
Cell service
Reliable
What's at the trailhead
- Restrooms — Vault toilets
- Water spigot
- Information kiosk
- Reliable cell service
If the lot is full
Drive up Flagstaff Road to the summit lots — same $5 non-resident fee, different physical lots scattered across the summit zone.
Access road
Permit-machine accepts cards and cash; bring small bills. Summit Road steep + winding — light vehicles recommended.
When to go
Highlighted months offer the best conditions.
Who shares the trail
Flagstaff's summit-zone open meadows host a regular ground-squirrel population that draws coyotes at dusk. The lower switchback trail through ponderosa is good Abert's-squirrel and mule-deer viewing year-round.
- Common
CommonAbert's squirrel
Sciurus aberti
Year-roundPhoto: USFWS — public domain
CommonWyoming ground squirrel
Urocitellus elegans
Summit meadows colonize with these chubby ground squirrels April through September.
Photo: USFWS — public domain
OccasionalCoyote
Canis latrans
Year-roundDawnDuskNightDrawn to the summit ground-squirrel colony at dusk.
Photo: USFWS — public domain
What to watch for
What to watch for
- Switchbacks cross Flagstaff Road repeatedly — watch for vehicle traffic
- Icy in winter and shoulder season without traction devices
- Informal climber tracks at trailside bouldering rocks — don't follow off-trail
- Afternoon storms during monsoon weeks (July–August) — turn back by 1 PM
On the map
Overnight camping
Day-use only — overnight not permitted
OSMP day-use only. Picnic shelters at the summit are for day-use; no overnight camping permitted.
Trail-tested picks for Flagstaff Mountain
Curated for this trail's terrain, elevation, and typical conditions.
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