From 1955 to 1965 the United States Navy employed Guardian-class radar picket ships (converted under SCB 126 from the former boxed aircraft transport version of the Liberty ship) to create barrier lines off the East and West Coasts. Eight were homeported at Treasure Island, California and eight at Davisville, Rhode Island. The ships' names matched the mission: USS "Guardian" (AGR -1), USS "Lookout" (AGR-2), USS "Skywatcher" (AGR-3), USS "Searcher" (AGR-4), USS "Investigator" (AGR-9), USS "Outpost" (AGR-10), USS "Protector" (AGR-11), and USS "Vigil" (AGR-12) on the East Coast and USS "Scanner" (AGR-5), USS "Locator" (AGR-6), USS "Picket" (AGR-7), USS "Interceptor" (AGR-8), USS "Interdictor" (AGR-13), USS "Interpreter" (AGR-14), USS "Tracer" (AGR-15) and USS "Watchman" (AGR-16) on the West Coast. The hull classification symbol of the ships was initially YAGR, changed to AGR in 1958. The standard crew consisted of 13 officers, eight chief petty officers, and 125 enlisted.