Crystal Springs Dam

Crystal Springs Dam is a concrete gravity dam that rises about 140 feet above San Mateo Creek and spans roughly 600 feet across the waterway. The structure holds back water to form the Lower Crystal Springs Reservoir and sits beneath Skyline Boulevard.

The dam was built in 1888 and stood as the tallest in the United States at that time, also marking the largest concrete structure in the world. It was developed as part of the water system to support San Francisco's growth.

The structure reflects a time when local engineers took on ambitious water projects to serve growing communities. It shows how large concrete works became central to regional infrastructure development in the region.

The location is easily reached via Skyline Boulevard, which passes directly over the structure and allows vehicle access to the area. The site also serves as a trailhead for hiking and biking activities along the scenic Sawyer Camp Trail.

The dam sits about 300 yards from the San Andreas Fault and has survived both the 1906 San Francisco earthquake and the 1989 Loma Prieta earthquake without significant damage. This demonstrates the strength of its original construction despite its proximity to one of the country's most active fault lines.