The Colfax Half Marathon takes runners on the eastern portion of the full marathon course. Starting at Ferril Lake in City Park, the route heads east through the Denver Zoo's famous "Zoo Mile" before looping back through Capitol Hill and downtown Denver.

The half marathon is the most popular Colfax distance, drawing over 10,000 runners annually. The course is flat-to-rolling and fast, making it an excellent choice for first-time half marathoners and PR seekers alike.

Altitude Advisory: At 5,280 feet, oxygen levels are about 17% lower than at sea level. Arrive 2–3 days early, increase water intake by 50%, and start conservatively.

Ready to Run?

Registration for the 2026 Denver Colfax Marathon is open.