Denver's only marathon — 26.2 miles, part of the May 15–16, 2027 race weekend, starting and finishing in City Park.
runcolfax.org has 2027 registration open through RaceRoster but does not publish a bib-transfer or deferral deadline yet. We watch the race's own registration page for when a transfer or deferral window opens and alert the moment it does.
Checked Sep 19, 2026 against the target's own page.
Watched from runcolfax.org, the target's own public page — not a reservation system we poll.