The great 1906 San Francisco earthquake destroyed key portions of the City of San Francisco’s water system, and the three days of unquenchable fires that followed claimed more than four square miles of land, thousands of buildings, and an untold number of lives. That devastation spurred city leaders to pursue a more reliable source of water. After intense national debate over building a reservoir and dam in a national park, Congress passed the Raker Act in 1913, granting San Francisco rights-of-way and the use of public lands to build the Hetch Hetchy Water and Power Project, despite opposition led by John Muir, who wanted the valley left untouched for wilderness preservation. The complex system of tunnels, pipelines, and facilities took 20 years to build and carries snowmelt 167 miles entirely by gravity, without pumps. Phase I of O’Shaughnessy Dam was completed in 1923, and phase 2 ended in 1938 when the dam was raised another 85.5 feet to a height of 312 feet. The reservoir now holds 117 billion gallons of water, the equivalent of 177,914 Olympic-sized pools, and today the system serves more than 2.4 million people in four counties in the San Francisco Bay Area as well as the residents of Groveland.