USS Cyclops (AC-4) was the second of four colliers built for the United States Navy several years before World War I. Named after the Cyclops, a 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 some time after 4 March 1918 remains the single largest loss of life in the history of the United States Navy not directly involving combat. As the loss occurred during World War I, she was thought to have been captured or sunk by a German raider or submarine, because she was carrying of manganese ore used to produce munitions, but German authorities at the time, and subsequently, denied any knowledge of the vessel. The Naval History & Heritage Command has stated she "probably sank in an unexpected storm", but the cause of the ship's loss is not known. History Cyclops was launched on 7 May 1910, by William Cramp & Sons of Philadelphia and placed in service on 7 November 1910. Operating with the Naval Auxiliary Service, Atlantic Fleet, she voyaged in the Baltic from May to July 1911 to supply Second Division ships. Returning to Norfolk, Virginia, she operated on the east coast from Newport, Rhode Island, to the Caribbean, servicing the fleet. During the United States occupation of Veracruz in Mexico in 1914–1915, she coaled ships on patrol there and received the thanks of the U.S. State Department for cooperation in evacuating refugees. With American entry into World War I, Cyclops was commissioned on 1 May 1917. She joined a convoy for Saint-Nazaire, France, in June 1917, returning to the U.S. in July. Except for a voyage to Halifax, Nova Scotia, she served along the East Coast until 9 January 1918, when she was assigned to the Naval Overseas Transportation Service. She then sailed to Brazilian waters to fuel British ships in the South Atlantic, receiving the thanks of the U.S. State Department and Commander-in-Chief, Pacific. Disappearance The ship put to sea from Rio de Janeiro on 16 February 1918, and entered Salvador on 20 February. Two days later, she departed for Baltimore, Maryland, with no stops scheduled, carrying the manganese ore. The ship was thought to be overloaded when she left Brazil, as her maximum capacity was . Before leaving port, Commander Worley had submitted a report that the starboard engine