Endure Trail Runs

The Endure Trail Runs take place in Mueller State Park in Divide, Colorado, in mid-May. The headline challenge is a 12-hour race in which participants draw colored balls to decide their loops. Other options are a marathon of about 26.5 miles, a half marathon of about 14.1 miles and a 10K of about 6.8 miles, on courses that run on double-track and single-track trails with no pavement.

The marathon and the 12-hour race start at 8:00 a.m., and the half marathon and 10K at 9:00. The time limits are accommodating, and a well-equipped aid station operates throughout the event. The park sits above 9,000 feet, where mid-May can bring cold, snow patches and thin air, so leave time to acclimate and carry layers.