Free Solo,” the acclaimed climbing documentary about a hair-raising summit of El Capitan, has crossed the $10 million mark at the box office. It now ranks as the fourth highest grossing documentary of the year, behind “Three Identical Strangers” ($12.3 million), “RBG” ($14 million), and “Won’t You Be My Neighbor?” ($22.6 million).

The film follows Alex Honnold as he climbs a 3,000-foot vertical rock face in Yosemite without using harnesses, ropes, or other gear. Directors Jimmy Chin and Elizabeth Chai Vasarhelyi spent years following Honnold as he meticulously planned his ascent, capturing him in intimate moments and finding new answers to the age old query “why does a man climb a mountain?”

“Alex’s climb is about living the best life you can,” Chai Vasarhelyi said. “The climb is about working through your fear.”

Shooting “Free Solo” raised ethical questions for the filmmakers. They worried they were encouraging Honnold to do something that could cost him his life. As he wrestled with his doubts, Chin reached out to his friend, the writer Jon Krakauer, for advice. Krakauer was familiar with the world of climbing, having written the Everest saga “Into Thin Air.”

“Jon asked me, ‘is he going to do it whether or not you film him?'” said Chin. “I answered with yes. Then he asked, ‘are you in the best position to shoot it and do you believe he can do it?’ And the answer to both of those questions was also yes. I’ve been working in this space for 20 years, I’ve seen the greatest athletes at the peak of their performance, and I’ve never seen anybody perform like Alex under high-stakes situations.”

Indeed, part of the raves for “Free Solo” haven’t just been for its compelling portrait of a stunning feat of athleticism.  They’ve focused on the filmmaking challenges of capturing Honnold’s ascent.

“What it took to make this film is just extraordinary,” said Courtney Monroe, president, National Geographic Global Networks, the company behind “Free Solo.” “This crew is the only one that could make this film. They’re not just elite climbers, they’re also world class cinematographers.”

“Free Solo” continues Nat Geo’s drive into the documentary space. Two years ago, the media company began dipping its toe into the non-fiction feature film waters, and has previously released “Jane,” a look at primatologist Jane Goodall, and “Science Fair,” the story of high schoolers competing for an international prize. “Free Solo” has been the company’s widest release, screening in more than 400 locations. It’s a smart time to get into the documentary space. Four non-fiction films took in more than $10 million at the box office this year, three more than hit that mark in 2017.

“We’re in a golden age of documentaries,” said Monroe.

Many of the films that have been hits have focused on compelling personalities such as Honnold, Fred Rogers, or Ruth Bader Ginsberg. The films that haven’t worked, namely Michael Moore’s anti-Trump picture “Fahrenheit 11/9,” haven’t offered much in the way of a break from the political drama in Washington. “Free Solo” literally rises above today’s partisan divides. Monroe thinks that may be part of the reason that the film is resonating with audiences.

“It’s an inspiring story,” said Monroe. “It’s about making the impossible possible and in this crazy chaotic world that’s an amazing message.”