San Dimas Dam

San Dimas Dam is a concrete gravity structure in Los Angeles County that creates a retention basin behind its concrete wall. The water flows through or is diverted to another reservoir instead of being stored permanently in this location.

The structure was built in 1922 when the county flood control agency constructed it to manage overflows from San Dimas Creek. This project was part of the region's broader effort to address seasonal water challenges.

The structure demonstrates how early engineers in Southern California managed and controlled water to protect the region from flooding. Visitors can observe how the construction fits into the landscape and what practical role it plays in the daily life of the surrounding area.

The site is typically open and viewable from nearby paths, though access restrictions should be respected. The best time to visit is after winter storms when the basin fills with water and the structure's function becomes visible.

The structure functions so that water seeps into the ground after storms instead of being held there permanently. This approach naturally replenishes groundwater supplies for the region.

Location: Los Angeles County

GPS coordinates: 34.15500,-117.77194

Latest update: December 14, 2025 13:04