Registration for the 2026 Denver Colfax Marathon opened Tuesday, with next year's event being the 20th year for the largest marathon weekend in the Rocky Mountain region.

Marathon weekend takes place May 15-17, and will also feature several other races in addition to the marathon, including a half marathon, a 10-miler and four marathon relay divisions, according to a news release from the Denver Colfax Marathon.

During the marathon's 20-year lifespan, runners have raced a total of 3 million miles throughout the city, according to the release. The event has grown significantly in size during that time period too, surging from just 4,000 runners to over 25,000.

"Over the past 20 years we’ve seen this event become a source of motivation for thousands of runners in our community," Andrea Do

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