Running the Colfax Marathon: Tips for Registration and How To Prepare

The Colfax Marathon is Colorado’s largest running event by far, bringing tens of thousands of athletes and spectators to downtown Denver for a springtime weekend of racing and revelry. More than just a race, it’s like a big running festival that shows off all the great food, live music, and outdoorsy energy that Denver is known for.

You don’t have to run 26.2 to join in the fun, but Colfax is a legendary race that as a marathoner you won’t want to miss out on. The course features major Denver landmarks with a backdrop of the snowy Rocky Mountains, and it’s one of the country’s highest urban races at 5,280 feet above sea level. That’s why entering the Colfax Marathon is the perfect way to test yourself as a runner while enjoying all the best of the Mile High City.

RELATED: How To Train for a Marathon

Here is the essential information you need to know about signing up for the Colfax Marathon, along with other Colfax races that you can enter. Learning details like the race dates, features of the course, and a bit more about Denver will help guide your marathon training and prepare you for your trip to Colorado.

Colfax Marathon Route

This race is Colorado’s original marathon, and the course holds a reputation as one of the most beautiful urban race routes in the country. The marathon traces Colfax Avenue — America’s longest main street — through a mix of historic districts, verdant parks, riverside paths, and iconic landmarks of the Mile High City. Here are just some of the highlights:

• Green lawns of City Park and a pass by the gates of the Denver Zoo.

• A lap around Empower field in Mile High Stadium, where the Denver Broncos play.

• Confluence park, where two rivers come together in the heart of downtown.

• A jog through Firestation #1, where a crew of firefighters waits to cheer you on.

• Several miles alongside flowing water of Cherry Creek, the South Platte River, and Sloan’s Lake.

• A mix of historic and modern architecture throughout the city, including the eclectic shops and restaurants along Colfax Ave.

• Majestic Rocky Mountain views along much of the course.

It’s a challenging yet rewarding course, perfect for runners who want the test of altitude while enjoying all the best perks of a big-city marathon weekend.

How to Register for the Colfax Marathon

Signing up for the Colfax Marathon is relatively simple. You don’t need to have participated in a marathon previously, or in any other race for that matter. You simply need to register through Race Roster in advance of the event. As of 2024 there is no hard deadline for registration, however there is an early registration pricing window. This means that if you sign up early you will get a cheaper entry. Check the Colfax Marathon website and RaceRoster.com for the most up-to-date information about registering.

Other Denver Colfax Races 

Besides the Colfax Marathon, there are several other running and walking events that take place the same weekend. These include race distances from 5k to half marathon, and there’s even a marathon relay for completing 26.2 as a team. Here are all the Colfax races, as of 2024, and a bit about what to expect from each.

Colfax 5K

The 5K is a family-friendly race in City Park, adjacent to the zoo and the course of the other races. This event is meant to be truly for everyone. It has multiple waves, one of which allows small children and strollers. Another wave allows dogs. There is also a competitive wave, however, and it’s a chip-timed race so you can make the 5K as serious or as casual as you like.

RELATED: How To Train for a 5K

Urban 10 Miler

This race follows the last 10 miles of the marathon course, earning highlight locations like Mile High Stadium and Confluence Park. It overlaps in time with the marathon, but a later and staggered start means that 10-mile racers get to file in with the marathoners and experience all the same energy at the finish line.

Colfax Half Marathon

This is the race with the famous “Zoo Mile.” The Colfax Half Marathon loops one mile through the Denver Zoo, where runners go by giraffes, kangaroos, bears, and many other animals in their enclosures. The second half of the race takes Colfax Ave past the capitol building and into downtown, so runners get a taste of Denver’s best urban scenery as well.

RELATED: How To Train for a Half Marathon

Colfax Marathon Relay

The Colfax Relay is set up for teams of runners to complete the marathon course as a team. For the relay, the 26.2-mile course is divided into five legs for individual runners to complete. The relay has divisions for teams of employees from companies, government agencies, or public schools, and there is also an open relay for teams of any five runners.

Colfax Marathon Frequently Asked Questions

Planning to register for the Colfax Marathon, but still have more questions? Here is some additional information that’s pertinent to the 2025 race.

When is the Colfax Marathon?

The Colfax Marathon takes place annually in May. The 2025 race weekend is May 17-18, with the marathon and most of the other races happening on Sunday, May 18 2025.

Is the Colfax Marathon Denver’s only marathon?

At the time of writing, the Colfax Marathon is the only official marathon held within Denver city limits. However, some other marathons take place in nearby cities and other areas of Colorado.

Do you need to qualify for the Colfax Marathon?

The Colfax Marathon is open to runners of all abilities, and there is no requirement to pre-qualify. Registration typically opens in the fall and spots can fill up, so be sure to sign up early if you want to enter.

How many people run the Colfax Marathon?

The 2024 Colfax Marathon saw nearly 25,000 participants, and more than 50,000 people gathered in total for the festivities of marathon weekend. 

What is the Colfax Marathon time limit?

The Colfax Marathon has a time limit of six hours for completing the full marathon course. This works out to an average pace of 13:44 per mile. Runners who fall behind this pace will be asked to stop for safety reasons.

Is the Colfax Marathon a Boston Qualifier?

Yes, as a certified marathon race, the Colfax course is a Boston Qualifier. Runners who achieve a Boston Marathon qualifying time at the event will be eligible for Boston and perhaps for other marathon majors as well.

Does the Colfax Marathon go through the Denver Zoo?

No, the Colfax Marathon course does not currently run through the Denver Zoo, but the half marathon does. Runners who enter the 13.1-mile Colfax race will be treated to the famous “Zoo Mile” in the first half of the course.

Colfax Marathon Training Tips

Running any marathon is a feat that requires lots of specific training, but Denver’s marathon presents an extra challenge – the "Mile High" elevation. At nearly 5,300 feet above sea level, you will certainly feel the altitude when running if you aren’t acclimatized. There are ways to prepare for this in your marathon training, however. Here are some essential tips.

• Build a strong base: This is crucial for any marathon, but for Denver it is especially important to put in consistent training for overall fitness, not just pace or mileage. This is because your entire body will feel the rigors of altitude, but a strong base fitness will help carry you through.

• Embrace hill work: Denver's terrain makes for several climbs on the marathon course, so incorporating hill repeats and strength training for your legs and core are crucial. The better power and stability that you gain from hill work can help carry you through the final grueling miles in Denver.

• Join a running group: If you live nearby, consider joining one of Denver’s many road running clubs to help you train and get tips from Colfax Marathon veterans. Even if you live elsewhere, running with a local crew is just as helpful for training motivation and support leading up to your race. 

• Arrive in Denver a week early: If you are able to make it happen, spending time in Colorado before the race will do wonders for adjusting to altitude. Your body naturally acclimatizes in a handful of days, and you can speed this up by going on light jogs and walks around the city or nearby trails.

Denver is a city that’s famous for its outdoors and for its athletic culture, so the Colfax Marathon adds another big reason for runners to come and experience it. With the right attention to training and preparation, you can conquer your race distance in Denver while thriving on the mountains of energy here in Mile High City.