Old Mission Dam: the 200-year-old stone dam hiding in Mission Trails

Mission Trails Regional Park is mostly known for its peaks, but at its northeast corner there's something older than California statehood: a stone dam across the San Diego River, still holding back a pool of water two centuries after it was built. It takes about two minutes to walk to from the car, and it's one of the oldest engineering works in the West.

California's Office of Historic Preservation says the dam and its flume were built between 1813 and 1816 by Native laborers, historically Kumeyaay, working with Franciscan missionaries. The goal was a reliable water supply: the dam diverted river water down a gravity-fed flume about 6 miles to Mission San Diego de Alcalá, the first of California's missions, for crops and livestock. Recurring floods damaged it beyond repair by around 1831, and after the missions were secularized it was abandoned. It was registered as California Historical Landmark No. 52 on December 6, 1932.

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Old Mission Dam

1. 1Old Mission Dam trailhead parking — Off Father Junipero Serra Trail
2. 2Old Mission Dam — Built 1813-1816

Nearby

1. 3Mission Trails Visitor Center — 1 Father Junipero Serra Trail

Pins are approximate. Source: California Office of Historic Preservation and OpenStreetMap, checked October 6, 2026.

See these on the full San Diego map

• —Size: about 244 feet long and 13 feet thick, stone and cement set on bedrock (Hidden San Diego).
• —Lot hours: Hidden San Diego lists 8 a.m. to 5 p.m. from November through March and 8 a.m. to 7 p.m. from April through October.
• —Free: no entry or parking fee.
• —Look for the remains of the flume and the pool still held behind the wall.