1951: Air Defense Command 1960: United States Navy USN/FAA radar: Mount Thirst Ground Equipment Facility J-36A (San Clemente Island Air Force Station until 1960) is a Federal Aviation Administration (FAA) radar station of the Joint Surveillance System (JSS) in the Western Air Defense Sector (WADS) of NORAD.

In World War II, Los Angeles Harbor Defenses included posts on some islands of Southern California, e.g. in March 1942, "a 200-man Army detachment set up two radar stations" on San Clemente Island, and in March 1944, Navy "Seabees built two permanent radar installations[where?]

As with other Air Defense Command stations replaced by facilities of the joint-use site system (JUSS), San Clemente Island AFS was replaced in 1960, and 670th operations moved to the JUSS RP-39 station at San Pedro Hill AFS with barracks at Fort MacArthur near the Project Nike direction center (part of the Los Angeles Air Defense Area).

)[opinion] In 1966 (July 30-August 9), field activity D-4-66-SC of the United States Geological Survey in the Coastal and Marine Geology Program used San Clemente Island with a Western Electric M-33 radar for a study of the Bathymetry and Structure of San Clemente Island (e.g., the "CURV vehicle of Naval Undersea Research and Development Center, was...used for seafloor sampling.

")[5] In 1972 south of the former AFS, the Navy installed an AN/FPS-20 general surveillance radar at Mount Thirst (32°53′03″N 118°27′03″W / 32.88417°N 118.45083°W / 32.88417; -118.45083 (San Clemente Island J-36A)).