MORGAN COUNTY, Tenn. (WATE) — The 36th Barkley Marathons began Tuesday morning in Frozen Head State Park.

The event is made up of 100 miles of running and climbing through the mountains. The course is made up of five 20-mile loops, and participants only have 60 hours to complete the entire route. Only 15 people have completed the feat since the race was created.

Gary Cantrell, also known as “Lazarus Lake,” co-founded the race with his friend Karl “Raw Dog” Henn in 1986.

“It’s about twice the climb of climbing Mount Everest from sea level, it’s on a lot of unmaintained trails, there’s no course markings, the runners have to carry everything they need to survive each 20-mile loop,” Cantrell said as he described the route.

The race began shortly at 9:54 a.m. Tuesday morning, marked by Cantrell lighting a cigarette. Front-runners, including John Kelly, completed the first loop of the race around 6:15 p.m. Kelly was the most recent person to finish the race, back in 2017.

Only 40 runners are invited to participate each year, and Kelly is not the only returning competitor. Jared Campbell is running this year and has completed the race three times. Jasmin Paris is running the race for the second time and is the first woman to do so since 2013.

The runners have very limited resources while completing each route.

“They have to use a map and a compass and their skill in the woods to navigate their way around, and it’s all day and all night for two and a half days,” Cantrell said.

For the first three years of the race, the course only stretched around 50 miles and had a 24-hour time limit. “Frozen” Ed Furtaw was the first to complete that route in 1988.

“At the time, I was able to run most 50-mile races in about eight hours, so I was amazed to see that here was a 50-mile race with a 24-hour time limit and no one had finished it,” Furtaw said.

He said Cantrell came up with the idea for the race after James Earl Ray’s infamous prison escape from Brushy Mountain State Penitentiary in 1977. The prison sits just near the bottom of the mountain where the race takes place.

“In 54 hours, he was only about eight miles from the prison, so Gary and his friend ‘Raw Dog’ Karl Henn, they were familiar with the mountains here, they hiked and camped here, and Gary said, ‘In that amount of time I could have done 100 miles,’” Furtaw said.

This year marks the 36th Barkley Marathons, as a few years were missed due to the COVID-19 pandemic and other park-related issues. Furtaw has attended 25 of the races and said Cantrell continues to evolve the event.

“He says, ‘I’m trying to keep it at the limit of what’s possible.’ He’s trying to keep it at the limit of human endurance, so that’s why he adjusts the course,” he said. “He makes it harder when people finish it, and if it goes a few years where no one can finish the 100 miles, he backs it off a little bit, he’s really kind of a creative genius.”

Furtaw wrote a book about the marathons, “Tales From Out There: The Barkley Marathons, The World’s Toughest Trail Race.” The marathon also gained international attention after a documentary was made about it in 2014. The film is titled, “The Barkley Marathons: The Race That Eats It Young,” and eventually landed on Netflix.

This year’s race included runners from various countries including Japan, Sweden and France.