Since debuting in 2006 with about 4,000 runners, the Colfax Marathon has grown into the largest running event in Denver and the largest marathon weekend in the Rocky Mountain region, drawing 25,000 runners in 2024 across seven races including a marathon, half marathon, urban 10-miler, and 5K, plus a Boston Marathon-qualifying course.
Colfax Avenue is not, on its face, an obvious choice for a marathon course.
This marathon's route is built around a single, unglamorous urban corridor, Colfax Avenue, long known as one of the longest commercial streets in America, and turns it into the backbone of a race that has become Denver's largest running event
The weekend now includes seven separate races and a two-day health and fitness expo, anchored by a marathon relay that ranks as the second largest marathon relay in the United States, while a signature Zoo Mile lets runners pass directly through the Denver Zoo grounds partway through the course
The marathon continues a tradition
established at its 2006 founding
of using Colfax Avenue
one of the country's longest and most historically significant commercial corridors
as the organizing spine of a major regional running event
while its Boston Marathon-qualifying status ties it into the broader national distance-running community
Dates TBA · Usually May
Base the route around Denver, then leave extra time for temporary streets, queues or late return traffic.
Late May in Denver can range from warm and sunny to unexpectedly cold or wet at altitude, so layered running gear, a throwaway jacket for the start, and altitude-appropriate hydration...
For Colfax Marathon, choose safe viewing points, watch weather and leave extra time around starts, finishes or releases.
For peak dates, book flexible lodging near reliable routes into and out of Denver.
Check official or local sources for ticketed areas, paid stands, and same-year access rules.
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Colfax Marathon is listed for Past edition: 16–17 May 2026. Always re-check the official or local source close to travel.
The festival is listed in Denver, United States. The map coordinate is a planning reference, not a guarantee of a ticket gate or exact venue.
2 days is the listed festival span. Add time for arrival, local transport, queues, and any route changes during the event.
Official source linked. Eventisimus separates source confidence from travel suggestions, so check final details before booking.
Denver, CO
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