This is a list of all monitors of the United States Navy. While the most famous name is represented in this list, many monitors held multiple names during their service life. View the complete . The whole category of monitors took its name from the first of these, USS Monitor, designed in 1861 by John Ericsson. They were low-freeboard, steam-powered ironclad vessels, with one or two rotating armored turrets, rather than the traditional broadside of guns. The low freeboard meant that these ships were unsuitable for ocean-going duties and were always at risk of swamping and possible loss, but it reduced the amount of armor required for protection.