USS Monitor became the prototype of a form of ship built by several navies for coastal defence in the 1860s and 1870s and known as a monitor. It was a low freeboard, mastless steam-powered vessel with one or two rotating armoured turrets. The low freeboard meant that these ships were unsuitable for ocean-going duties, but had the advantage that there was less area to cover with armour and the sea washing over the deck in heavy weather would keep the vessel stable.
A more seaworthy variation was called the breastwork monitor, and had the turrets and any superstructure mounted on a raised platform. These were not particularly successful as sea-going ships, because of the short range caused by the low efficiency and poor reliability of the steam engines of the day. The first of these ships was the HMVS Cerberus, built in 1868 to 1870 and which still exists (in rather poor condition) near Melbourne, Australia.
Attempts were made to design variations of these ships which were fully rigged to overcome both the technical and the cultural problems of relying upon a steam engine (naval tradition in the larger navies of the time meant that steam power was looked down upon).
These were mostly unsuccessful because the rigging interfered with the turrets' 360 degree arc of fire and because of problems with the ships' stability caused by the combined weight of turrets and masts above the waterline. However, the monitor did eventually evolve into the battleship.
The monitor as a class of warship reappeared in a rather different form during the First World War as a flat bottomed sea-going barge equipped with battleship-sized guns and intended for bombardment of the enemy coast, an example of this type of monitor is the Royal Navy Monitor M33. Several of these ships were still in existence, and a few more were built, to play a part in the Second World War.
There was also a class of river monitors — the strongest dedicated river warships.
A late example of a monitor-type ship is the Huascar, a Peruvian Navy ship that was the vessel commanded by Admiral Miguel Grau during the war between Peru and Chile (War of the Pacific, as it is known in those countries) in 1879. After a long series of battles, the Huascar was captured by the Chilean Navy at the battle of Punta Angamos, October 8th 1879, during which most of the Huascar's crew died, including Admiral Grau. The captured ship, where in May of that year Captain Arturo Prat of the Chilean Navy died after a unequal battle between the Huascar and the wooden, sail ship Esmeralda, was commissioned into the Chilean Navy, and is currently at dock in Talcahuano, still a commissioned vessel with crew and commanding officer. It is available for visits.
List of monitors of the Royal Navy