In 1905, when the city of San Francisco lobbied Congress to allow it to dam the Hetch Hetchy Valley to provide the growing city with water, Muir and Colby were leaders of the campaign to prevent the damming of the Tuolumne River and the flooding of the valley.
In 1905, when San Francisco lobbied Congress to permit it to dam the Hetch Hetchy Valley for water supply, Muir and Colby were prominent figures in opposing the construction of a dam on the Tuolumne River and the flooding of the valley.