Clyde began climbing in the Sierra Nevada in 1910, when he visited Yosemite and Sequoia National Parks, writing to his mother that I climbed the highest mountains in the region. He also visited McCloud, near Mount Shasta, that summer. He began a regimented program of mountaineering in the Sierra Nevada in 1914, including the first of his first ascents. He also joined the Sierra Club in 1914. He first climbed Mount Shasta in 1916, and climbed that peak a total of 12 times. While living in Southern California during his wife's illness, he climbed Mount San Jacinto in 1917. Following his wife's death in 1919, he climbed extensively in the Kings-Kern Divide region of the southern Sierra.