Colfax Marathon

Registration is open to all and handled through Race Roster. It typically opens in August for the following May's race. Prices increase as the race date approaches, so registering early saves money. There is also a charity entry option through more than 100 charity partners.

Yes, the course is USATF certified and qualifies for Boston. Keep in mind the race is run at altitude with 600 feet of cumulative gain, so conditions are not ideal for fast times. Plan your goal pace accordingly.

It's a multi-loop course through Denver that stays between roughly 5,100 and 5,500 feet of elevation throughout. The route accumulates 600 feet of gain with no net downhill to compensate, so expect rolling terrain and the added effort of running above a mile high.

The time limit is 6.5 hours.

May mornings in Denver can be cold at the start, sometimes in the low 40s, warming into the upper 60s by midday. Bring a throwaway layer for the start and plan your hydration strategy for a warming second half.

The race starts and finishes at City Park in Denver. Denver International Airport is about 25 miles away, roughly 45 minutes by car or RTD transit. Free RTD transit is included with your race bib, which makes getting to and from the start area straightforward.

Recent editions have seen roughly 2,900 finishers in the full marathon. It's a mid-size field that feels manageable without being too small.