The Hetch Hetchy Reservoir, located on the Tuolumne River in Yosemite National Park, was built to provide water and hydroelectric power to San Francisco. Its creation in the early 1900s led to one of the first conflicts between preservationists and those favoring utilitarian use of natural resources. The controversy spanned the presidencies of Roosevelt, Taft, and Wilson.

A prolonged conflict between San Francisco and its only water utility, Spring Valley Water Company, drove the city to search for an independent water supply. After surveying several possibilities, the city decided to build a dam and reservoir in the Hetch Hetchy Valley because the river there could supply the most abundant and purest water. This option was also the least expensive, since the city planned to use the dam to generate hydroelectric power. It would also provide an abundant supply of irrigation water for area farmers...