RunSignup has released its 2025 ultramarathon statistics report, and the headline finding is that the ultra format is still growing faster than the rest of the American running economy. Races using the RunSignup platform saw an 8.3% increase in ultramarathon participation in 2025, against an average of 5% growth across all race distances on the same platform. Averaged over all 418 races in the report's sample, per-event ultra participation was up 6.5%, and the gap between ultras and shorter road distances — where half marathons and 10Ks have both slowed since 2023 — continues to widen.
Geographically, the growth story remains weighted toward the American south and mountain west. Forty-six states hosted at least one ultramarathon on RunSignup's platform last year, but Texas, Colorado, California and Utah accounted for a disproportionate share of the 728 events and 50,220 participants captured in the report. Texas in particular is now the single largest ultra state by race count, propelled by winter and shoulder-season events that capitalise on mild December-to-March temperatures in the Hill Country and the Chihuahuan Desert. Colorado and Utah's share is driven more by summer mountain races, while California's numbers are shaped by both Sierra Nevada point-to-points and the Bay Area's dense weekend trail-race calendar.
The demographic findings reflect a sport that is still skewed male at its longer distances, with men making up 65% of 50K entrants and 76% of 100-mile entrants, but the gap narrows meaningfully at timed-hour formats — 44% of six-hour entrants and 46% of 24-hour entrants are women. RunSignup's analysts attribute the gender balance at timed events to three factors: a lower cut-off risk, a more controlled racing environment, and a stronger crossover from the walking, run-walk and ultra-community populations where female participation is already near 50%. By comparison, the hardest-to-enter 100-mile trail events remain the most male-dominated segment of the sport.
Two other trends in the data reward a closer read. First, the growth in mid-sized events (250–500 finishers) has outstripped growth in both small and very large races, pointing to a maturing club-race tier that sits between grassroots backyard events and the UTMB-affiliated flagship series. Second, 24-hour and backyard-format events together grew by roughly 14% in 2025, more than twice the average ultra growth rate, as the format's social-media-friendly shape and its accessibility for both road and trail runners have widened its appeal. The report also notes that RunSignup's sample tends to undercount destination trail events that use Ultra-Signup or bespoke registration, so the overall picture for American ultramarathoning is likely stronger still.
For race directors and gear brands, the practical takeaways are familiar: women's participation at timed-hour and sub-50K ultra distances is the fastest-growing segment, which has implications for everything from shoe size curves to on-course nutrition. For national federations, the geographic concentration of events in the southern and mountain-west states matches the USATF map of qualifying races for the IAU 100K and Trail World Championships, and arguably strengthens the case for federal-level travel support for athletes from under-represented regions. The raw numbers, taken together with Ultrarunning Magazine's parallel estimate of roughly 150,000 finishers across 3,270 events industry-wide, suggest that American ultramarathoning finished 2025 at or near its all-time participation high.