Survey of Historic Sites and Buildings
Ownership and Administration. City of San Diego.
Significance. Old Mission Dam, whose associated aqueduct and flume extended about 5 miles to the Mission of San Diego de Alcalá, was one of the first major irrigation engineering projects on the Pacific coast of the United States. It impounded water from the San Diego River, and for much of the year provided an assured supply, which was released as needed for agricultural and domestic purposes.
San Diego de Alcalá Mission, founded by Father Junípero Serra July 16, 1769, on Presidio Hill, was the first of the 21 California missions. In 1774, Serra moved the mission 6 miles to its present location, both to free his Indian neophytes from the adverse influences of the presidial garrison and to obtain a location affording more water. Despite a native rebellion in 1775, the mission became one of the wealthiest and most populous in California.
New structures were erected during the period 1776-80, and by 1800 more than 1,500 Indian neophytes were attached to the mission. Earthquake damage in 1803 led to further rebuilding and enlargement. By 1813, the mission had assumed its present form. In 1824, the maximum population of 1,829 Indians was attained, but in 1835 they dispersed when the Mexican Government secularized the mission, after which the buildings were neglected and deteriorated rapidly.
The precise dates of construction of Old Mission Dam, as well as the aqueduct and flume, cannot be ascertained. Not likely begun before 1800, the dam was probably started in 1803, following a 2-year drought. By 1817, it had certainly assumed its final form. Of solid masonry, it was about 220 feet wide, 13 feet thick at the bottom, and 12 feet or more high. Native stone and locally produced cement were used to construct the dam, aqueduct, and flume. The flume, 2 feet wide and 1 foot deep, conducted water to the mission gardens and vineyards some 5 miles distant.
Present Appearance. By 1867, the dam and the aqueduct-flume system were reportedly in ruins. About 7 years later, they were repaired and again put to use. The remains of the dam, still impressive today, impound a small amount of water. The dam will be included in San Diego's proposed Fortuna Mountain-Mission Gorge Metropolitan Park. No substantial remains of the aqueduct or flume are visible. San Diego Mission has been largely reconstructed since 1931. 
NHL Designation: 05/21/63
Last Updated: 22-Mar-2005