Donkeys were an important part of the mining industry in the early days of the gold rush era, and the Cripple Creek Donkey Herd is made up of the direct descendants of the donkeys who spent their lives making trips up and down the mountain. Miners would typically set their donkeys free when they had to leave the area, and today the donkey herd roams freely through the gold camp. To celebrate the contribution the donkeys made to the town, a donkey derby is held every June, where participants lead donkeys through an obstacle course in a race to the finish line.