The Barkley is considered one of the toughest 100 mile races in the world. It has 52,900 feet of climb (and 52,900 feet of descent), more than any other 100 mile race, more than the 33,000 ft. of climb at
Hardrock, and more than the 45,000 ft. at
Nolan's 14. Since the race began in 1986, only 7 runners out of about 650 have finished within the 60 hour cutoff.