The contract for "Canonicus", the first Navy ship to be named for the chief of the Narragansett Indians, was awarded to Harrison Loring; the ship was laid down in 1862 at their Boston, Massachusetts shipyard. She was launched on 1 August 1863 and commissioned on 16 April 1864 with Commander E. G. Parrott in command. The ship's construction was delayed by multiple changes ordered while she was being built that reflected battle experience with earlier monitors. This included the rebuilding of the turrets and pilot houses to increase their armor thickness from to 10 inches and to replace the bolts that secured their armor plates together with rivets to prevent them from being knocked loose by the shock of impact from shells striking the turret. Other changes included deepening the hull by to increase the ship's buoyancy, moving the position of the turret to balance the ship's trim and replacing all of the ship's deck armor. As far as is known the ship was not modified after her completion.