USS Ajax (1864)
 Originally named USS Manayuk after a town in Pennsylvania USS Ajax was a single-turreted Canonicus-class monitor built for the Union Navy during the American Civil War. Completed after the end of the war Ajax was laid up until 1871 although she received her new name in 1869. The ship was briefly activated in 1871 before a much longer commission began in 1874–75. She was assigned to the North Atlantic Squadron during this time. Ajax was again placed in reserve in 1891.