Blue Sky Marathon & Half
About this race
The Blue Sky Marathon & Half runs the trails between Horsetooth Mountain Park and Devil's Backbone Open Space in Fort Collins. The course is 100% dirt and about 90% sweet Colorado single-track, from smooth trail to technical rock gardens. Marathon Saturday Oct 17; Half Sunday Oct 18.
Choose your distance
Marathon
What's included in your entry
- Well-marked course on premium Fort Collins trails
- Enthusiastic, knowledgeable volunteers and fully stocked aid stations
- Free Larimer County Open Space entry for race day (one vehicle park pass)
- Generous time cut-offs
- Gender-specific race t-shirt, unique finisher award and age-group awards
- Finish-line meal — vegetarian, vegan & gluten-free options
- Professional medical and emergency communications
The course
The course runs the trails between Horsetooth Mountain Park and Devil's Backbone Open Space — 100% dirt and ~90% single-track, from smooth trail to technical rock gardens.
Marathon: 26.7 mi / 3,500' gain — 22 mi dirt single-track, 3 mi rocky single-track, 2 mi dirt road. Half: 13.4 mi / 1,800' gain — 13 mi dirt single-track, 0.5 mi dirt road.
All aid stations provide Gnarly Fuel2O, Hammer gels, water and soda, salty and sweet snacks, and fresh fruit, plus vegetarian/vegan/gluten-free alternatives on request.
Race weekend timeline
Aid-station cut-off times
| Marathon · Blue Sky (mi 9.2) | 10:00 am (3:00 elapsed) |
| Marathon · Indian Summer S out (mi 15.6) | 12:30 pm |
| Marathon · Indian Summer S in (mi 20.3) | 1:45 pm |
| Marathon · Finish (mi 26.7) | 4:00 pm |
| Half · Finish (mi 13.4) | 1:00 pm Sun |
If you're not leaving an aid station by its cut-off you'll get a ride back to the finish. Sweeps leave at cut-off, taking course markings with them.
Carry a minimum 16 oz water bottle or bladder (refillable at stations).
Aid stations
Marathon (8): Towers 4.4, Blue Sky start/finish 9.2 (drop bag), Indian Summer N 13.2, Indian Summer S 15.6, Hunter turnaround 17.9, Indian Summer S 20.3, Indian Summer N 22.7, Finish 26.7 (drop bag).
Half (5): Underpass 1.9, Indian Summer N 5.4, Indian Summer N 8.1, Underpass 11.6, Finish 13.4.
Getting there & lodging
Directions
- Marathon start/finish — Blue Sky Trailhead, 4780 W CR-38E, Fort Collins (across from Horsetooth Tavern). Park at the Inlet Bay Marina lot; 0.7-mi walk to start. Carpools of 2+ get priority parking.
- Half start/finish — South Bay Pavilion, 4210 W CR-38E (park at South Bay). All registered runners get one vehicle park pass; crews need a Larimer County annual or $10 day pass.
Camping & lodging
- Camping at Horsetooth Reservoir's Inlet Bay (marathon) and South Bay (half) campgrounds. Fort Collins hotels for every budget are 20–30 min from the start.
Good to know
- Marathon limited to 9 hrs, half to 6 hrs; both start 7:00 am. Bib visible; call your number at each aid station; check out if you drop.
- Purposeful littering is immediate disqualification; stay on trail. Pacers not allowed; crewing at Blue Sky (mi 9.2) only. No dogs on course.
- Transfer credit: 100% until Mar 31, 75% to Jul 31, 50% to Oct 15 — valid 12 months. Half runners can upgrade to marathon for a fee; downgrade free.
Awards
All finishers receive a unique finisher award. Overall top 3 men's/women's and non-binary each distance; age-group top 3 in Under 40, 40–49, 50–59 and 60+.
Discounts, deferrals & transfers
Plans change. Discounts, deferral windows, and bib-transfer rules are the same across every Gnar Runners race — see the details on our Discounts & Deferrals page.
Who puts this on
Directed by Gnar Runners. Questions? Email racedirector@gnarrunners.com.