The San Juan Capistrano Mission Buildings were built beginning in 1778.  The principal structures existing include the church, two warehouses, a shop, military barracks, the missionary quarters, and kitchen.

In 1783 the military commander requested that a water supply system be built.  Water system included closed gravity water conduits for transporting fresh water to the Mission facilities from a nearby stream.

The buildings are the oldest known standing unreinforced structures in California.  Constructed utilizing adobe brick as a structural material and arch design.  Oldest planned industrial center in California.  Industrial operation included tallow making, wine making, wrought iron foundry, weaving mills, brick and tile firing, a grainary, cheese factory, and cattle raising.

The San Juan Capistrano Mission was designated as an Orange County Local Historical Civil Engineering Landmark in 1992 and a bronze plaque was presented at the site in 1993.