Colfax Marathon

Denver's largest annual running event, founded in 2006 and known as the Denver Colfax Marathon (title-sponsored by Cigna Healthcare for the race weekend). The full marathon starts and finishes at City Park on the east side of Ferrill Lake, running an 'Ultimate Urban Tour of Denver' that passes twice through Empower Field at Mile High, through Denver Fire Station #1 (the only marathon in the world to run through a working fire station), along seven miles of rivers and lakes including Sloan's Lake, and through downtown Denver and historic Lakewood with Rocky Mountain views. The course sits at Denver's mile-high elevation (roughly 5,170-5,530 feet / 1,575-1,685 meters), a genuine high-altitude challenge for endurance runners; the route is a rolling, largely flat-to-gentle profile with the main climb between miles 6 and 13 and a net-downhill return. It is an official Boston Marathon qualifier with a 6-hour time limit. The same race weekend also includes a half marathon, Urban 10 Miler, marathon relay (corporate, government, public school and open divisions), and a Colfax 5K. The 2026 edition marked the race's 20th anniversary, drawing 25,000+ participants across all weekend events.