High Quality Content by WIKIPEDIA articles! USS Cyclops (AC-4) was one of four Proteus-class colliers built for the United States Navy several years before World War I. Named for the Cyclops, a primordial race of giants from Greek mythology, she was the second U.S. Naval vessel to bear the name. The loss of the ship and 306 crew and passengers without a trace sometime after 4 March 1918 remains the single largest loss of life in U.S. Naval history not directly involving combat. The cause of the ship`s loss is unknown.