Beginning his career as a world-class mountaineer with more than 70 first ascents to his credit, Brower came to the environmental movement through his interest in mountaineering. In 1933, Brower spent seven weeks in the High Sierra with George Rockwood. After a close call with a loose rock while climbing in the Palisades, he met Norman Clyde in the wilderness, who gave him some valuable climbing lessons. On that trip he also met Hervey Voge, who persuaded him to join the Sierra Club. On May 18, 1934, along with Voge, he began a ten-week climbing trip through the High Sierra, to survey climbing routes and maintain mountaineering records for the club. Previously, they had established several food caches along their planned route, which began at Onion Valley and ended at Tuolumne Meadows. In all, the pair climbed 63 peaks on this trip, including 32 first ascents. On the first day, they climbed Mount Tyndall, Mount Williamson, and Mount Barnard. From June 23 to 26, the pair made eight first ascents in the Devils Crags along with Norman Clyde, and also climbed Mount Agassiz. Clyde called the Devils Crag climbs one of the most remarkable mountaineering feats ever accomplished in the United States. In the Palisades range, the pair climbed Thunderbolt Peak, traversed to North Palisade by way of Starlight Peak, and descended the U-Notch Couloir. In the Sawtooth Range, they climbed The Doodad, the West Tooth, and Matterhorn Peak.