Boulderthon Marathon

Location: Boulder
Country: United States
Website: https://www.boulderthon.org/
2025 Marathon Date: 28/09/25
2026 Marathon Date: 27/09/26
Winning Time 2025: 02:21:00
% Sub-3s: 0.5–1%
# Sub-3s: 10–49
Total Runners: 1k–3k

The Boulderthon Marathon is a relatively new but ambitious race staged in Boulder, Colorado. Known for its vibrant running culture and endurance pedigree, Boulder provides a striking setting for marathon racing, with a course designed to combine city landmarks with surrounding open roads.

The course is measured and certified but carries the inherent challenge of altitude. At over 5,000 feet above sea level, even well-trained runners notice the reduced oxygen availability, which places a premium on controlled pacing and efficient energy use. The profile itself is fair, with mostly flat sections and some undulation, but the thinner air adds difficulty that directly affects sub-3 ambitions.

Organisation has quickly gained praise: Boulderthon integrates a festival-style atmosphere with professional race management, providing strong aid station support and efficient logistics for participants. Crowd support is lively in central Boulder, particularly at the finish, reflecting the city’s deep connection to distance running.

For sub-3 athletes, Boulderthon is not a pure time trial. The altitude is the defining factor, demanding both respect and preparation. Those who adapt well and hold steady effort can still achieve their goals, but success depends as much on physiology and discipline as it does on speed.