About This Race
The High Lonesome 100 stands as one of Colorado's most challenging high-altitude ultras, traversing the rugged Sawatch Range where peaks pierce the thin air above 14,000 feet. Set in the heart of the Rocky Mountains near Nathrop, this loop course demands respect from even seasoned mountain runners as it climbs to a maximum elevation of 13,150 feet with over 23,500 feet of total elevation gain. The race follows some of Colorado's most pristine singletrack, winding through alpine meadows, across windswept ridgelines, and along sections of both the Continental Divide Trail and Colorado Trail. With 16 aid stations strategically placed throughout the 100-mile journey, runners have ample support as they navigate this remote and exposed terrain. The generous 37-hour cutoff acknowledges the technical nature of the course and the physiological challenges of sustained effort at altitude. Limited to 250 participants, the High Lonesome 100 attracts runners seeking an authentic mountain experience away from the crowds of more accessible races. The July timing offers optimal weather windows, though mountain conditions remain unpredictable above treeline. This is mountain running at its most demanding, requiring solid high-altitude experience and strong hiking skills for the sustained climbs.
The 100-mile loop course showcases the raw beauty of the Sawatch Range through predominantly singletrack terrain. Runners traverse sections of two of America's premier long-distance trails—the Continental Divide Trail and Colorado Trail—while climbing through multiple life zones from montane forests to alpine tundra. The course reaches its apex at 13,150 feet, where runners experience the stark beauty and physical demands of high-altitude running.
With nearly 24,000 feet of climbing distributed across the century distance, the course features sustained ascents and technical descents that demand both fitness and mountain craft. The terrain composition of 97% trails and paths with minimal road sections ensures an authentic backcountry experience throughout the loop back to Nathrop.
Elevation Profile
The course gains 23,501 ft over 101 miles, with the steepest section between mile 54–mile 54.
Course Map
Route shown is approximate and for illustration purposes.
Practical Info
July conditions typically feature warm days and cool nights, with afternoon thunderstorms common above treeline and temperatures potentially dropping below freezing at high elevations.
COS - Colorado Springs Airport
Limited lodging options in small mountain community of Nathrop; many runners camp or stay in nearby Salida or Buena Vista.
Best For
Notable Features
The High Lonesome 100 distinguishes itself through its combination of extreme altitude, pristine wilderness setting, and passage along two of America's most celebrated long-distance trails. The race's maximum elevation of 13,150 feet places it among the highest 100-mile races in North America, while its location in the less-traveled Sawatch Range offers solitude rarely found in Colorado's ultra scene.
Prepare for This Race
GEAR GUIDE
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A tested guide to the best hydration vests for ultra marathons and long trail races — from lightweight racing vests to high-capacity mountain packs.
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