Climbing some of the world’s most challenging mountains without the elements or the male-dominated alpine world stopping her: that’s what Miriam O’Brien Underhill wanted to do—and it’s just what she did.

In the 1920s, in the wake of the Great War, the world was in transition: new technologies were being introduced, the first signs of globalization were appearing, and the emancipation of women was accelerating—after all, women working in factories had propelled the wartime economy. In this atmosphere of new freedoms and possibilities, Miriam O’Brien indulged her urge to experience nature’s majesty by spending her weekends and holidays exploring the peaks and valleys of New Hampshire’s White Mountains however she could—whether that was in hiking boots or on wooden skis. Her successes didn’t escape the notice of New England’s close-knit network of mountaineers. As the climber’s fame grew, she was increasingly invited to join others on expeditions and became part of a community of like-minded people.

Although O’Brien had the skills and drive to push herself emotionally and physically, her gender held her back. The rules of the day stipulated that women couldn’t summit alone or lead expeditions—they needed men to get them to the top. But this didn’t satisfy Miriam: “Very early I realized that the person who invariably climbs behind a good leader may never really learn mountaineering at all and in any case enjoys only a part of the varied delights and rewards of climbing.”

O’Brien’s desire to climb mountains independently never waned. She could deal with setbacks due to the elements, because she actually preferred challenging routes and weather conditions—that was just part of mountaineering. But being hindered from reaching her full potential by the male-dominated culture of the alpine world? That was an obstacle she was determined to break through.

By 1927, O’Brien was confident in her ability to make a guideless—that is, manless—climb. And she succeeded, summiting the Grépon, one of the toughest climbs in the Alps. Sadly, the reaction of French mountaineer Étienne Bruhl to this great achievement was typical of male alpinists in that era: “The Grépon has disappeared. Of course, there are still some rocks standing there, but as a climb it no longer exists. Now that is has been done by two women alone, no self-respecting man can undertake it. A pity, too, because it used to be a very good climb.”

Poor Étienne had to add many more iconic peaks to his list of “climbs that no longer exist”. Miriam went on climbing—with other women and with Harvard professor Robert Underhill, her future husband—and eventually summited many peaks in the US, the Jungfrau and Mönch in Switzerland, and the Matterhorn (three times!). She left a huge outdoor legacy: she not only broke barriers, but also mapped climbing routes and wrote climbing reports that are still used today.

Miriam O’Brien Underhill scaled the alpine heights not only because of her inner fire and unquenchable thirst for adventure, but also because of the simple joy she took in being outdoors. In discovering completely new routes up some of the world’s most challenging mountains, she showed us that adventure is in our nature—and it’s in all of us, regardless of gender. Her success in overcoming the hardships of mountain-climbing and the glass ceiling put up by other alpinists sends a clear message to us all: Whatever challenges you might face on your way to the top are only there to be overcome.