This past Sunday, John Kelly won one of the hardest races in the United States, if not the world. The Washington D.C. native was the first and only finisher of the 2017 Barkley Marathons, a 100-plus-mile race, in 59:30:33. He came in only 27 seconds before the 60-hour race cut-off. In doing so, he became the 15th person to ever complete the race.

The Barkley Marathons is not your typical race—or even your typical ultramarathon. Started in 1986 by Gary “Laz” Cantrell and Karl Henn, the course runs through the woods of Frozen Head State Park in Tennessee. Runners must complete five loops of the course in less than 60 hours. Three loops completed in less than 40 hours is known as a “fun run.” There are no aid stations, except for two water tables.

The course is dotted with books that serve as checkpoints, much like a timing mats in a traditional road race. Runners take the page corresponding with their bib number to prove they have followed the course. Bib numbers change with every loop.

Entry is limited to 40 runners. Although each loop is supposed to be 20 miles, most competitors maintain that the distance is closer to 25.

The conditions for the race were brutal—bitterly cold with snow and fog. According to Running Magazine, Kelly finished wearing a Walmart bag and orange hat that he found along the course after passing out.

Kelly had company for most of the race. He ran the first four loops with Gary Robbins of North Vancouver, British Columbia. They were the only runners to make it beyond the fun run stage of the race. Runners must alternate directions for the 5th and final loop. Kelly chose to go clockwise, requiring Robbins to go counter-clockwise.

A navigational error on the trail caused Robbins to omit 2 miles from the loop and finish in the wrong direction. However when he finished, Robbins was told only told he missed the cutoff by six seconds, causing a heartbreaking scene. Race director Gary Cantrell later cleared up the mistake on Facebook.

Next year’s race should take place March 31-April 1. Gaining an elusive bib number to the Barkley Marathons is just as tough as finishing. Entry deadlines and requirements are closely guarded secrets.

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