Tommyknocker 12-Hour & The Mine Shaft Half

The Tommyknocker 12-Hour & The Mine Shaft Half takes place at Mueller State Park in Divide, Colorado, in mid-May, as part of the Human Potential Running series of Endure trail races. The main event is a timed 12-hour race in which runners are assigned loops at random. Participants can run as long as they want within the 12 hours, and results are based on the total distance covered.

The program also includes a 10K of about 6.8 miles, a half marathon of about 14.1 miles and a marathon of about 26.5 miles. The marathon and the 12-hour race start at 8:00 a.m., and the shorter races at 9:00. All courses use double-track and single-track trails with no pavement, and a dedicated aid station supports runners. At this elevation, expect thin air and variable mountain weather.