Boulder Field 100

Boulder Field 100 is a trail ultra organized by Uber Endurance Sports in Jim Thorpe, Pennsylvania, on September 12, 2026. Three formats are offered: a 100K (62 miles) starting at 5:00 AM, a 50K (31 miles) at 7:00 AM and an 18 Miler (29 km) at 7:30 AM. The name is a fair warning that rocks are part of the deal.

The 18 Miler is a good option for trail runners who want more than a half marathon without going full ultra, and the 50K is a classic first-ultra distance. The 100K is a serious step that rewards runners with a 50-mile finish already in hand. Whichever you pick, spend your build on technical trails to protect your ankles and your pace, add back-to-back long runs for the longer distances, and practice hiking the steep bits with purpose rather than forcing a run.