Catch all the racing action of the Mammoth Trailfest on the Sept 25-27 Mountain Outpost livestream.
Trail running has no shortage of destination races and festivals, but few events pack in as much substance, scenery, and community vibes as the Mammoth Trailfest. Held every September in the Eastern Sierra Nevada mountains at the height of the fall color season, the multi-day gathering has grown from a niche mountain event into one of the most complete trail running experiences in the country—part elite competition, part community celebration, part small-town block party.
Here are a few things that set this year’s event apart. You can watch it all unfold via the daily livestream produced by Mountain Outpost.
1. World-Class Terrain, Late-September Timing, and a Race for Every Level
Mammoth Trailfest takes place in late September at Mammoth Mountain ski area, timed to catch the Eastern Sierra at its most spectacular before winter sets in. The event spans five distinct races: the 3-mile Dragon’s Back Ascent hill climb, the 50K, the 26K, a 10K fun run (called the “tenkay”), and Woolly’s 1K kids’ race, along with a grueling 200-mile ultra (starting a week later, on October 2) for those chasing the outer edge of endurance. That range and highly generous 12-hour cutoffs to support all ability levels means the festival draws everyone from first-time trail runners to seasoned mountain athletes onto the same weekend calendar.,
2. A Genuine Commitment to Inclusivity
Trailfest has built inclusivity into its DNA rather than treating it as an afterthought, a commitment reflected in a race weekend that welcomes a broad and diverse community of runners. This year, that commitment takes a historic step forward: the event has partnered with Born to Adapt to offer free para/adaptive entries to the 26K and introduce what’s believed to be trail running’s first-ever prize purse for adaptive athletes. It’s a meaningful signal that Trailfest sees adaptive competitors as elite athletes worth funding, not just including. Plus, it has a clear, progressive transgender registration policy.
3. The Largest 50K in the U.S., on a Course Built to Showcase Mammoth
Trailfest’s 50K has grown into the largest race of its distance in the country (642 finishers last year), pulling in veteran ultrarunners and elites alongside first-timers testing themselves on real mountain terrain. What makes it special isn’t just the size of the field—it’s the intent behind the course. Designed as a single loop with no repeated sections, the 50K weaves together smooth singletrack, rocky technical trail, volcanic pumice, and stretches of bike path, delivering nearly 7,000 feet of climbing at an average elevation above 9,100 feet. Rather than piling on difficulty for its own sake, the course is built around scenery, flow, and accessibility, turning a demanding mountain ultra into a showcase of everything that makes Mammoth special.
4. Run up the Mountain, Get Half a Donut at 11,500 Feet
The Dragon’s Back Ascent may be short on paper, but it delivers one of the most distinctive experiences in American trail running. At just 3.5 miles with 2,400 feet of gain to the summit of Mammoth Mountain at 11,050 feet, it’s California’s highest hill climb—a steep, lung-burning sprint straight up the mountain. The reward at the top is as memorable as the climb itself: fresh donuts waiting for runners at the summit party, turning a brutal vertical effort (and sometimes frigid weather) into one of the weekend’s most beloved traditions. But with 400 runners and 200 donuts in this year’s ascent, it means every only gets a half a donut. So not exactly a recovery meal, but still something fun after the finish.
5. A Genuine Community-First Personality
Trailfest is built around bringing runners, families, volunteers, and spectators together rather than isolating racers from everyone else. It is both a local event for trail runners in the Eastern Sierra—it goes out of its way to let locals sign up first—and a destination event that draws runners from the Los Angeles, Oakland, and San Francisco running communities as well as places much farther afield.
Free town shuttles, family-friendly programming, post-race recovery areas, and community activities all run throughout the weekend. Trailfest pairs its races with live music, films, storytelling, food, talks, and even a stand-up comedy show this year. That mix means Trailfest works as a destination even for people who never plan to toe a start line—friends and family can experience the full weekend right alongside the runners in their lives.
The event operates on U.S. Forest Service land with a strong emphasis on trail etiquette and minimizing environmental impact. Ultimately, it’s a race weekend designed as much for the people cheering on the sidelines as for the ones running the course.
6. A Field With National Talent—and Rising Stars
Trailfest has become a magnet for serious competitive talent, drawing elite ultrarunners to its 50K and 26K races each year, alongside a deep, competitive field chasing podiums and prize money. Some of the top athletes racing this year include Emily Clarke, Charlotte Cheyne, Dayna Stimson, Peyton Bilo, Grant Colligan, Sean Handel, Cole Watson, Zoe Rom, Adam Sjolund, and Bradley Revenis.
Among this year’s most compelling storylines is 13-year-old Pema Franchi, an Ecuadorian trail runner who—as well as her 22-year-old brother Noam Franchi—has rocketed from newcomer to podium regular in mountain racing in just two and half years, most recently with four race wins in Europe. Pema, will take on both the Dragon’s Back Ascent hill climb and the 26K at Trailfest, events she placed among the top five in last year as a 12-year-old, while Noam will run the 50K.
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