Denver’s City Park pulsed with excitement as more than 20,000 runners, ranging from seasoned marathoners to eager first-timers, converged for the 20th anniversary of the Colfax Marathon on May 16 and 17, 2026. For two decades, this event has grown into the Rocky Mountain region’s largest running celebration, and this year’s edition proved to be a milestone worthy of all the fanfare.
The festivities kicked off on Saturday morning with a 5K race, drawing early risers and families to City Park. But it was Sunday that truly showcased the marathon’s scope. At 6 a.m. sharp, the full marathon, half marathon, Urban 10 Miler, and marathon relay all set off from City Park, sending waves of runners through Denver’s most iconic landmarks. The course wound past Sloan’s Lake, along historic Colfax Avenue, through the heart of downtown, and even ventured inside the Denver Zoo and Empower Field at Mile High. It’s not every day you get to run through a football stadium or past dragon boats on a city lake!
“A 20-year milestone deserves a big celebration,” said Andrea Dowdy, chief executive of the Denver Colfax Marathon, in a statement to the Denver Post. Dowdy reflected on the marathon’s origins, recalling, “In the beginning, it was actually a regional effort by the mayors in Denver, Lakewood and Aurora to say, ‘How can we celebrate Colfax Avenue?’” That vision has blossomed into a tradition that now draws athletes from around the globe and thousands of spectators lining the streets to cheer every step.
This year’s marathon boasted more than 40 on-course attractions, ensuring there was never a dull moment for runners or fans. From live music and cheer squads to themed relay handoffs, the energy was palpable. “The wows actually vary significantly. For example, we have a couple of wows that are our big tradition, such as running through the stadium and running through Denver Zoo,” Dowdy explained. Dragon boats glided across Sloan’s Lake, kayakers paddled the South Platte River, and aerial acrobats and musicians kept spirits high. The coordination of so many moving parts is no small feat. “The coordination is actually very elaborate, not only for the person who's recruiting all the talent, but also placing them, making sure they have everything they need, timeframes, logistics, and that type of thing,” Dowdy said to Denverite.
With so many participants and fans, the city of Denver and the Regional Transportation District (RTD) had to make major adjustments to keep things running smoothly. On Sunday, from 5:30 a.m. to noon, several light rail and bus lines operated on detours or saw temporary service interruptions. The D and H light rail lines skipped service between Colfax at Auraria Station and the Downtown Loop, while the L Line was out of service entirely, with bus Route 43 stepping in as an alternative. Bus routes 0, 1, 6, 8, 9, 10, 12, 15, 15L, 16, 19, 20, 24, 28, 30, 38, 40, 43, 44, 48, 51, 52, 76, 83L, ART, and FREE all faced detours and delays, making for an unusually quiet downtown for drivers—but a bustling scene for runners. RTD even sweetened the deal for participants, allowing official race bibs to serve as valid fare on the W Line and bus routes 15, 15L, and 16 from 6 a.m. to 2 p.m. Sunday.
Of course, the marathon’s impact extended far beyond the finish line. The event’s Charity Partners Program, now the second-largest in the country after the New York City Marathon, partnered with more than 200 nonprofits and has raised over $5 million since its inception. Youth initiatives like Fly Feet and Girls on the Run brought local children into the fold, inspiring the next generation of runners. Colorado’s fastest competitors vied for a share of a $22,560 prize purse, with a $1,000 bonus up for grabs for anyone breaking an event record.
Behind the scenes, more than 2,000 volunteers powered the weekend, handling everything from bib distribution at the expo to handing out bananas and water at the finish line. “We’ll have over 2,000 volunteers on race weekend, which is terrific and people can sign up online to volunteer to do all sorts of things, whether it's handing out bibs at the expo or whether it's handing out a banana at the finish line or serving water, lots of opportunities,” Dowdy said. Their enthusiasm was matched by thousands of spectators, who lined the course with homemade signs and relentless cheers. Dowdy fondly recalled her favorite sign from a previous year: “Go, stranger, go!” She added, “They didn’t even know anybody in the race. They just wanted to get out there and cheer.”
Among the many inspiring stories on the course was that of Rob Woodbury, a Denver local who’s run every day since January 1, 2021. “I started running on Jan. 1, 2021, and have been going ever since,” Woodbury shared. His streak spans nearly 2,000 consecutive days and includes runs in 14 countries. “Ever since 2021, I’ve run about a 5K every day,” he said. For Woodbury, running isn’t about competition or weight loss; it’s about discipline and mental health. “I think everyone should do something every day they don’t want to do, and that improves their mental health,” he explained. This year, he opted for the half-marathon, focusing less on speed and more on soaking up the unique atmosphere. “Most of the runs I’ve done in the past are for time. This one, I’m just trying to enjoy it and be a part of it.”
Weather always plays a role in outdoor events, and this year, the forecast was on the runners’ side—at least for the early hours. Denver7 meteorologist Stacey Donaldson predicted cooler temperatures and rain holding off until later in the day, setting the stage for near-ideal running conditions. Spots for the full marathon were still filling up as the weekend approached, a testament to the enduring appeal of the Colfax Marathon.
Rolling street closures impacted Colfax Avenue, downtown Denver, City Park, Sloan’s Lake, and stretches through Lakewood and Wheat Ridge. Interstate 25, Colorado Boulevard, and Kipling Street remained open, but drivers elsewhere were urged to plan ahead and expect delays. Full details on closures and event logistics were shared at runcolfax.org, ensuring everyone—runners, volunteers, and fans—could navigate the city’s biggest running weekend smoothly.
As the Colfax Marathon’s 20th anniversary unfolded, Denver once again proved why this race has become a beloved tradition. With its blend of athletic achievement, community spirit, and citywide celebration, the event left thousands inspired and already looking forward to next year’s adventure.