Designed by John Lenthall. The hull of the monitors were of a conventional form, but were constructed of wood, not iron. The ships displaced and were in length with a beam and draft. Freeboard was 31 inches, which left part of the hull exposed, this was covered several inches of armor plate backed by oak. The turrets, with of an armor, were similar to the turrets on the , only slightly larger. There were pilothouses fitted on the top of each turret. A light hurricane deck was constructed between the turrets, along with a tall funnel and a tall ventilation shaft. There were some variations within the class which leads some sources to identify them as four one-ship classes. One difference was that Tonawandas turrets were closer together than the other three ships in the class.
