Colorado is the densest mountain-ultra state in America. Three iconic 100s, a deep bench of 50Ks and 50-milers, and a year-round trail-running culture centered on Boulder, Salida, and Steamboat. If you're picking a Colorado race, here are the ones that matter.
The 100-milers
Hardrock 100
100.5 miles in the San Juan Mountains around Silverton. 33,000 ft of climb, six 13,000-ft passes, the most prestigious 100-miler in America. Read the Hardrock briefing →
Leadville Trail 100
100 miles starting at 10,200 ft, with two trips over Hope Pass at 12,600 ft. The altitude race. Read the Leadville briefing →
Run Rabbit Run 100
100 miles in Steamboat Springs. Two formats, Hare ($100K purse) and Tortoise (36-hour cutoff). The most spectator-friendly 100 in America. Read the Run Rabbit Run briefing →
The 50-milers and 100Ks
Silverton Alpine 50
50 miles in the same San Juan Mountains as Hardrock. ~13,000 ft of climb. Held in early August. The unofficial Hardrock training race.
Quad Rock 50
50 miles in Lory State Park, Fort Collins. ~12,000 ft of climb. May. A common Western States qualifier; runnable course; well-organized.
Run Rabbit Run 50
50-mile distance of the same Run Rabbit Run weekend. Same Steamboat course as the 100, half the distance. ~10,500 ft of vert.
Leadville Trail Marathon & Heavy Half
Marathon (26.2 mi, ~6,000 ft vert) + Heavy Half (15 mi, ~3,000 ft vert). Held in late June at altitude. Top finishers earn auto-entry to the Leadville Trail 100. The Leadville Race Series qualifier path.
The 50Ks worth knowing
Cheyenne Mountain 50K
Colorado Springs. ~5,500 ft vert. Late February. Fast, runnable course.
Sage Burner 50K
Gunnison. ~5,000 ft vert. May. A steady mid-elevation race; good first-50K option.
Black Canyon Ascent
Montrose. The hill-climb-only race up Black Canyon. Cult favorite.
North Fork 50K + 50M
Pine, CO. June. Excellent mid-summer mountain course. ~7,500 ft vert (50K) / ~13,000 (50M).
Where to live and train if you're chasing a Colorado 100
The three serious Colorado ultra-towns:
- Boulder: the most established. Trails out the door (Sanitas, Green Mountain, the Flatirons). Strong running club scene.
- Salida: the 14er + Collegiate Peaks training base. Cheaper than Boulder, equally good trails.
- Steamboat Springs: for the Run Rabbit Run / fall-season runners. Lower altitude than Leadville but real mountain access.
Why train in Colorado
Colorado's mix of altitude (most of the state sits between 5,000 and 10,000 ft) plus genuine mountain trails (rather than rolling Eastern hills) gives ultrarunners the closest American simulation of UTMB or Hardrock conditions. Most American ultrarunners targeting mountain races spend at least 2 weeks per year in Colorado.
What these sessions assume you are measuring with
Every pace, zone and power figure here needs something recording it. These three cover running, long days and the bike.
Garmin Forerunner 965 AMOLED multisport with the training-load and threshold metrics most of these sessions assume you can see day to day.
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COROS APEX 2 Series GPS Watch Sapphire titanium and the longest battery in its class, which is the deciding feature once a day out runs past a few hours.
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Favero Assioma Uno Power Meter Pedal Single-sided pedal power, the cheapest honest entry into training with watts rather than estimating from heart rate.
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