Denver's largest running event has arrived. The 19th annual Denver Colfax Marathon will feature several races over two days: Saturday, May 17, and Sunday, May 18. The weekend's events include a marathon, half marathon, 10 miler, and the nation’s largest marathon relay on Sunday. A 5K race will be held Saturday. Race organizers said that as of Friday, the marathon relay and half marathon are now sold out. Registration is still available for the marathon, Urban 10 miler and the Colfax 5K. Read more: https://www.9news.com/article/life/style/colorado-guide/denver-colfax-marathon-weekend-routes/73-e8e02a46-c73a-4274-b8bd-fd91c1dc024b