By most accounts, she was in high spirits. Having successfully climbed Mount Everest in May — unassisted and without oxygen, becoming the first woman to do so — Alison Jane Hargreaves now contemplated the peak of K2 towering over her in Pakistan’s Karakoram range. It was August 13, 1995, and she had a lofty goal: to become the first woman to ascend the three highest peaks in the world — Everest, K2 and Kangchenjunga, east of Everest — without supplemental oxygen. Under a cloudless sky, she left camp to check the second mountain off her list.

She never made it back down.

[Hargreaves] was a trailblazer, because she climbed Everest alone … while breaking down social constructs of what it means to be a mom. Molly Schiot, author and filmmaker

Some names will forever be synonymous with mountain climbing. George Mallory, Edmund Hillary, Tenzing Norgay, Reinhold Messner … these names are known by enthusiasts ranging from armchair mountaineers to accomplished alpinists. Far fewer remember the name Hargreaves.

She grew up in Derbyshire, England, the daughter of two mathematicians who early on instilled in her their love of walking the hills of England and Scotland. Another early influence was Hillary Collins, her outdoor pursuits teacher at Belper High School, who taught her how to rock climb at age 15. Three years later, having discovered her talent for climbing, she set up a mountaineering equipment company with James Ballard, whom she would later marry. Hargreaves made headlines in 1988 when, six months pregnant with her first child, Tom, she became the first female British alpinist to summit the north face of the Eiger in the Alps.

Becoming a mother did not end Hargreaves’ climbing career. In fact, her passion became a family affair. In 1993, two years before she made her attempt on K2, she became the first climber — male or female — to solo the six classic north faces of the Alps in a single season. Her family — husband James, son Tom and and daughter Kate — traveled with her, and she wrote about the experience in her 1995 book, A Hard Day’s Summer: Six Classic North Faces Solo.

Hargreaves wasn’t just breaking new ground in her sport; she was forging a trail socially as well. “[Hargreaves] was a trailblazer, because she climbed Everest alone without any [supplemental] oxygen while breaking down social constructs of what it means to be a mom,” says author and filmmaker Molly Schiot, who profiled Hargreaves in her 2016 book, Game Changers: The Unsung Heroines of Sports History.

Indeed, Hargreaves faced criticism when, following the release of A Hard Day’s Summer, she decided to begin her quest to climb Everest, K2 and Kangchenjunga, leaving two young children at home. She knew full well the risks associated with her audacious goal; she also knew she was one of the most talented climbers in the world. “Some of her alpine solos at the time were the cutting edge and today remain right up there with similar feats by the very best male alpinists,” says her son, Tom, himself a climber. “No woman has ever come close.”

That day in August the weather was favorable on K2, widely regarded as the world’s most dangerous peak, and so Hargreaves and five other climbers decided to go for it. Though the weather turned, bringing snowy conditions as a storm moved in, Hargreaves, along with Spanish climber Javier Olivar, radioed back to base camp to report that they had summited.

That was the last radio call Hargreaves made, disappearing from the mountain during her descent through treacherous winds. Other climbers who had turned back from a summit bid reported seeing her jacket, a pair of boots and a harness near her last known location — and in the distance, a body. To this day, Hargreaves’ body remains on K2; recovery excursions can be dangerous and are rarely attempted.

History is replete with climbers who never made it off the mountains they tried to climb. Their aspirations are typically treated with awe and respect. But Hargreaves’ death on K2 elicited a different response — namely, criticism that she would have risked her life (and ultimately, sacrificed it) climbing as a young mother.

But Hargreaves had pursued her passion with the blessing of her family; in fact, her son, Tom, followed in her footsteps. In 2015 he became the first person to climb all six of the great north faces of the Alps in winter. “I guess this career choice is not particularly surprising, considering the way I was brought up and my exposure to climbing and mountains before I was even born,” Ballard says. “Instead of being pushed away from the mountains by my mother’s death, I have been drawn toward them.”

According to Hargreaves’ husband, she lived her life by the words of an old Tibetan saying: “It is better to have lived one day as a tiger than a thousand years as a sheep.”

Only a tiger could have accomplished what Hargreaves achieved in her short career. Standing atop Everest’s summit without oxygen and unaided is no small feat. While more than 4,000 people have climbed the peak, fewer than 200 have done so without access to supplemental oxygen. That number was far smaller when Hargreaves did it in 1995. “I hope we all learn [Hargreaves’] story,” Schiot says. “It only makes us stronger.”

Paddy O’Connell, staff writer for Adventure Journal, agrees. “Hargreaves is one of the most accomplished mountaineers, and her story is inspiring,” adding that if Hargreaves’ name doesn’t come up in discussions about the all-time best alpine climbers, male or female, “it’s probably not a conversation worth participating in.”