Blue Sky Trail Marathon
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Event overview
The Blue Sky Trail Marathon and Half take place October 18-19, 2025 in Fort Collins, Colorado, running between Horsetooth Mountain Park and Devil’s Backbone Open Space. Distances offered:
- 26.7 miles (3,500 ft total gain/loss)
- 13.4 miles (1,800 ft total gain/loss)
The event has a registration cap of 400 entries for each distance and on-course time allowances of 9 hours for the marathon and 6 hours for the half. The course sits between about 5,300 ft and 6,500 ft elevation and includes wildlife such as deer, Abert squirrel, and golden eagle. Finish-line amenities include a meal, awards, and sponsor giveaways.
Course, aid stations and logistics
The courses are 100% dirt, with approximately 90% singletrack. Marathon terrain breakdown: 22 miles dirt singletrack, 3 miles rocky singletrack, and 2 miles dirt road. Half terrain includes 13.0 miles dirt singletrack and 0.5 miles dirt road. The route is marked with pink flagging, flour at key intersections, and confidence flags on longer stretches.
Aid stations are fully stocked with sports drink, water, gels, salty and sweet foods, fruit, and nearly all GF/vegan alternatives; utensils and cross-contamination cannot be guaranteed. Marathon runners may leave a drop bag at the Blue Sky start/finish to be available at mile 9.2; half marathon runners may leave a drop bag at the South Bay start/finish. Crewing and pacing rules differ by race - crewing on the marathon course is restricted to designated locations and pacers are not allowed. Runners must carry at least 16 oz of water; dogs are not allowed on course. Visit the organization's website for the most recent information.