Morris Reservoir is located in the San Gabriel Mountains about 5 miles north of the city of Azusa along California State Route 39. Morris Reservoir is below San Gabriel Reservoir. The mean elevation is about 1400 ft.

This site was a naval weapons test facility from WW2 to the early 1990?s. It was established by Caltech, which was developing weapons for the Navy at its Naval Ordnance Test Station at Ridgecrest, California (which today is known as the China Lake Naval Weapons Center, and which is still the primary proving ground for naval weapons systems). Because there is no lake to speak of at China Lake, Caltech opened this substation at the Morris Reservoir, in the San Gabriel Mountains, north of Azusa. This site was used especially for the development of submarine-based warfare systems, including torpedoes, bombs, and submarine-launched missiles like the Polaris rocket, the first ballistic missile that could be launched from submerged submarines. Most of the buildings at the site have been removed, and the site is being restored to a "natural" state, and may once again be open to the public.