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 8 runners out of about 700 have finished within the 60 hour cutoff. Mark Williams of the UK finished first in 1995 in 59:28. Here is his race report. In 2001, after several failed attempts, Blake Wood, 42, NM, and David Horton, 50, VA, finished together in 58:21, only to be disqualified for inadvertently leaving the course to follow a parallel route for about 200 yards. This route (on the south side of the stream instead of the north side) has slightly better footing and had been the normal route until 2000.
To give you some idea of the difficulty of this course, Blake had won the 2001 Rocky Raccoon 100 in 16:13, and the 1999 Hardrock 100 in 30:11. David Horton won Hardrock in 29:35 in 1993 and in 1991 set a course record for the Appalachian Trail, 2160 miles in 52 days.
Cave Dog (Ted Keizer) finished in 56:57 in 2003. He holds the Colorado 14er speed record, 54 14,000 ft. peaks in 10 days, 20:26. He also holds speed records in the White Mountains, Adirondacks, and Catskills. (See www.thedogteam.com). He trained for 2 weeks on the course before the race.
In 2004 Mike Tilden and Jim Nelson finished in 57:25 and 57:28, running the last loop in opposite directions as required by a rule added the year before. Both have finished Nolan's 14.
In 2008 Flyin' Brian Robinson set a course record of 55:42. He was the first person to hike the 3 major N-S U.S. trails in a single calendar year: Appalacian, Continental Divide, and Pacific Crest, 7400 miles in 300 days.
In 2009, Andrew Thompson finished in 57:37. In 2005 he set the current speed record for the Appalachian Trail, 2160 miles in 47 days + 13:31 (breaking Pete Palmer's record of 48 days + 20:11 in 1999, who took the record from Horton).
The Barkley consists of 5 20-mile loops with no aid except for water at two points. The cutoffs for the 100 mile race are 12 hours per loop. The 60 mile "fun run" has a cutoff of 40 hours, or 13:20 per loop. To prove you completed each loop, you must find 9 to 11 books (varies) at various points along the course and return a page from each book.