It impounds water in a rift valley created by the San Andreas Fault to form the Crystal Springs Reservoir.

A 2024 review by ASCE and the Institution of Civil Engineers in Great Britain indicated that it is likely the oldest mass concrete dam in the world.

Under the leadership of George Ensign, a prominent land baron, it quickly established a monopoly on the San Francisco water market.

[3] Understanding that any potential water source would have to come from outside of the naturally barren city limits, Ensign turned towards adjacent San Mateo County, along with its largely undeveloped mountains and streams.

[4] Geological testing was conducted using boring techniques, which showed that the valley was favorable for the dam's construction: the foundation was hard sandstone that contained no cracks or fissures.

[4] Schussler ensured that each block of the dam was poured with concrete made to the exact proportions of his mix specifications.

The City of San Francisco purchased the Spring Valley Water Company in 1928, through a $41,000,000 bond approved by voters.

[11] Another public funding grant from the City of San Francisco in 1933, intended to develop and expand the Hetch Hetchy Project, led to repairs and upgrades to the pump station, enabling it to pump a maximum of 70 million gallons per day to San Andreas Reservoir.

The San Francisco Public Utilities Commission, who owns the 23,000 acre watershed of the reservoir, began renovating the dam in 2003.

A major step in the renovation process, doubling the width of the main spillway and raising the dam to increase the water storage capacity, was completed in 2012.

It is unclear if Hermann Schussler, the chief engineer of the project, was aware of the existence of the San Andreas Fault 1,100 feet (340 m) away from the dam.

[16] The dam is also classified with an "Extremely High" downstream hazard rating by the California Department of Water Resources in the event of a breach.