Thank her or blame her, Cheryl Strayed and her mega-popular book Wild have turned thru-hiking into a mainstream national pastime, with trails like the Pacific Crest, Appalachian, and Continental Divide getting exponentially more popular—and crowded.

But there’s one great U.S. thru-hike that’s been mostly spared the influx. Few people have heard of, much less attempted, the Great Western Loop, a 7,000-mile route that patches together portions of the Pacific Crest, Pacific Northwest, Continental Divide, Grand Enchantment, and Arizona trails, with sections of trail-less walking through the Sonoran and Mojave deserts. No official designation exists for the Great Western, which traverses some of the West’s most beautiful, rugged, and remote terrain, dipping into nine states, 12 national parks and more than 75 wilderness areas.

Only one person has ever completed the epic—professional backpacker and guide Andrew Skurka, who started the Loop in California and ended in Arizona. Jeff Garmire, a 27-year-old from Vancouver, Washington, plans to be the second. And judging by the more than 5,100 miles he’s already completed, he’s got a pretty decent chance at success.

Although the Great Western Loop reaches some of the highest elevations in the U.S.—Garmire chose to summit 14,505-foot Mount Whitney—it’s not the terrain that makes it so daunting. “The biggest challenge of the GWL is a mathematical one,” Skurka told me this fall. The Sierra and San Juan mountain ranges stay buried in snow much of the year, raising the risk of blizzards and avalanches, and making long-distance backpacking gear untenable. “To do it in one shot, you have to complete about 4,600 miles of trail in about four months.” In other words, you have to hike the entire distance of the Appalachian Trail twice in less than the length of a single season.

Although the Great Western Loop reaches some of the highest elevations in the U.S., it’s not the terrain that makes it so daunting.

Garmire has already met that goal, an achievement that brought him much relief. “Since starting on April 29, I’ve been nervous about hitting Colorado early enough,” Garmire said when we talked in late September during his rest day in Silverthorne. Now that he’s reached Colorado? “I feel really good about it.”

Garmire started his long-distance hiking career in 2011, when he completed a thru-hike of the Pacific Crest Trail. There he earned his trail name, Legend, for hitching to town and back to bring his hiking friends pizza. “I grew up with a path in front of me, which is, you know, do good in high school, go to college, get a career, have a family, retire, close scene kind of thing,” he said. “It opened up this whole side door.” In 2014, after graduating college, he hiked the still-rugged 1,200-mile Pacific Northwest Trail. The following year, he took a job in Colorado, and spent the summer hiking every 14,000-foot peak in the state on the weekends. There are 58 of them.

His biggest achievement to date came in 2016, when he hiked the three crown jewels of American long-distance hiking—the Pacific Crest Trail, Continental Divide Trail, and Appalachian Trail, for a total of nearly 8,000 miles—in 252 days. He was the fourth man to ever complete the Triple Crown in a single year. (Accomplished long-distance backpacker Heather Anish Anderson is attempting to do the same this year. She would be the first woman to do so.)

Then 2017 was a bust. Other than some trail running and a race, Garmire didn’t have any big goals. “I had pretty good depression all year just because I didn't have this big thing out there that I was chasing,” he said. He wasn’t sure his body was up for logging hundreds and hundreds of miles under a backpack, yet he missed his long days outside.

He found a path back to that life in February, when he undertook a 100-mile round trip traverse across Zion National Park. He wanted to see if his body could take another beating. When he completed the route in less than 48 hours, he started looking at what he wanted to do next. He was drawn to the Great Western Loop because of how difficult it would be to execute, timing-wise. So in April, he quit his job as a small business consultant and began walking.

It’s a good year for the attempt, according to Skurka. California had a dry winter, making the Sierra less daunting. But that didn’t make it easy. “The Sierra Nevada was probably the hardest I’ve ever worked through anything,” Garmire said. On his daily adventure blog, Free Outside, he described post-holing up to his knees with each step around Pinchot and Mather Pass, the falling snow adding inches as he walked. Meanwhile, a small cut created an infection in his toe that put him in ongoing pain.

Other factors presented exhausting challenges, too. On the Pacific Northwest Trail, old burn areas made for tedious work crawling over downed logs and navigating barely-there trails, his body blackened in soot. Colorado had been a real ass kicker, too. “There's a lot of 3,000 foot climbs stacked on top of each other,” he said.

Garmire comes from an outdoorsy family, and he’s used to the comedy of errors that often comes with wilderness adventures. “I got giardia when I was a year old,” he explains. Not long after that, his parents tried to drop him off at daycare after a family backpacking trip. “They wouldn’t let me stay because they thought I had chicken pox, but I just had so many mosquito bites.”

While walking, he tries to make himself laugh. He tests out accents on himself—Liam Neeson, Donald Trump, Steve Buscemi. “These are only good enough for me to laugh at them,” he says. This year he ordered a sweatshirt with a large tiger face, which cracks him up when he sees himself in photos. He chuckles a little when he tells me about a family of hikers who saw him relaxing naked in a creek.

Still, it’s hard to imagine that fun is the only thing he’s after. After we get off the phone, Garmire decided to add an additional challenge to his route—hiking Nolan’s 14, a challenge to hike and scramble fourteen 14,000-foot peaks in Colorado on trails and cross-country scree slopes in less than 60 hours. He nearly fell asleep while hiking. He cliffed out multiple times, rolled his ankle, missed a junction, and lost the trail often. But he finished. “Toughest thing I have ever done,” he texted me the day after.

Skurka says there are two challenges ahead for Garmire: the Grand Canyon and the Gila Mountains in southern New Mexico, both of which, despite being desert, can hold their fair share of snow and make hiking treacherous. But that shouldn’t stop him, he says, because there are plenty of alternate options that would put him at lower elevations. “He's come a pretty long way to quit now,” Skurka says. “If he's hit with something, I think he'll probably figure it out and keep going.”

Now in New Mexico, Garmire was met with winter’s approach. Temperatures stayed below freezing and wind blasts covered half his face in icicles, frosting his glasses. But when I texted with him earlier this week, he sounded confident. “I have done a lot of snow hiking the last couple years, so I’ll make it through this one, too,” he writes. Meanwhile, he’s still got two states and 1,900 miles left.