William E. Colby's devoted service to the Sierra Club extended over more than 60 years. He joined the Sierra Club 1898, and served as its secretary from 1900 to 1946 (except for two years). In 1901, Colby conceived of the annual High Trips that began the Club's popular outings program, and he personally led these trips until 1929.
It was Will Colby who worked most closely with John Muir during the Sierra Club's campaign to save Yosemite National Park's Hetch Hetchy Valley from being flooded for a reservoir. After John Muir's death in 1914, Colby became a key Club leader and served as a director for 49 years. He contributed substantially to the saving of redwoods, to enlarging Sequoia National Park, and to establishing Kings Canyon and Olympic national parks. Colby was also the first chairman of the California State Park Commission in 1927.
In 1961, Will Colby became the first recipient of the Sierra Club's John Muir Award—its highest recognition for achievement in conservation.
William Colby died at his home in Big Sur, California, on November 9, 1964.
Ansel Adams wrote of him:
"You knew who he was without inquiry—he comes with him a deep humanity, and the mood of rivers and forests and clean white stone."