Trail Running calendar near Castle Rock 2025-2026

Niwot's Challenge is a highly demanding ultramarathon held annually in Sedalia, Colorado, along the South Platte River in the Front Range. Modeled after the grueling Barkley Marathons, it features a mostly off-trail course requiring advanced navigation skills using map and compass, with no GPS allow..

The Greenland Trail Races, held annually in May at Greenland Open Space in Larkspur, Colorado, offer four race distances: 4 miles, 8 miles, 25K, and the 50K ultramarathon, known as Colorado's fastest 50K. The course features wide, smooth dirt trails through native grasslands, ponds, oak hills, and p..

The Valkyrie Trail Race, held in Cheyenne Mountain State Park near Colorado Springs, Colorado, is a women-focused trail running event offering distances from 4 miles up to 50 kilometers. The course begins on crushed limestone meadows before transitioning to singletrack trails ascending Cheyenne Moun..

Endure Trail Runs, part of the Human Potential Running Series, is held annually at Mueller State Park near Divide, Colorado. The 6th edition in 2026 offers a unique 12-Hour timed event where runners draw colored balls to determine their next loop, running as many miles as possible within 12 hours. A..