High Lonesome 100
Mount Princeton, United States • 17-18 Jul 2026
Event overview
The High Lonesome 100 is a high-elevation, loop ultramarathon held in the Sawatch Range of the Colorado Rockies near Nathrop / Mount Princeton. The 2026 edition is scheduled for July 17-18. The event is organized by Freestone Endurance and has been held since 2017. The race takes place on lands administered by the San Isabel and Gunnison National Forests, Chaffee County, and the Colorado State Land Board, and it is fully permitted by the United States Forest Service and local authorities. The event uses a 37-hour time cutoff.
Course details
The course is a mountain loop of roughly 100 miles with approximately 23,000–23,500 feet of vertical gain and an average elevation just over 10,400 feet. The route starts and finishes at County Road 321 at the base of Mount Princeton and includes long sections of singletrack - about two thirds of the distance - plus mining, gravel, and some paved roads. The course includes:
- about 27 miles on the Continental Divide Trail
- about 35 miles on the Colorado Trail
The route crosses five alpine passes, goes above treeline for a significant portion, passes through two historic ghost towns, and traverses remote basins and exposed ridgelines. One notable feature is a sustained, rolling ridge section above treeline before Monarch Pass. The final portion follows long sections of the Colorado Trail back toward the start. Downloadable GPX, KML, and full course maps are available from the organizers for detailed route study. Visit the organization's website for the most recent information.