It spans the San Diego River, which was historically a seasonal body of water which dried out in the summer.

The dam created a body of water behind it, which would undergo controlled releases when the river otherwise ran dry.

A tile channel to the mission fields was also built, in order to minimize water loss in the sandy soil, but only fragments of this work still survive.

[5][6] Mission San Diego de Alcalá was founded in 1769 by Father Junipero Serra, and was moved to its present surviving site in 1774.

The works probably reached their greatest extent in 1817, including the tiled aqueduct and other features lost to time and vandalism.