Civil War Monitors

The Monitor was a prototype vessel, built for the Union Navy from a series of designs by John Ericsson. Sixty ironclad warships, modeled after the Monitor, were constructed by the federal government during the Civil War, and of these thirty-seven were actually commissioned. The design criteria called for shallow-draft, turreted, and ironclad gunboats. The ships built from these designs were intended to counter Confederate efforts to construct ironclad warships. They were designed to operate in shallow sounds and rivers against fortifications and ships guarding entrances to southern ports during the Civil War.

The two new batches of monitor-type ships, designed by Ericsson were in two classes of vessel: the Passaic Class and the Canonicus Class monitors. Both of these classes were improved and enlarged designs of the original Monitor, and each added about 25 feet in length: Monitor was 172 feet long, Passaic was 200 feet long, and Canonicus 225 feet long. The turret, which was initially mid-ships on the Monitor, progressively moved forward in the two later designs.

A third class of monitor, the light draft monitors commonly called the Casco class, was also developed during the Civil War but proved to be largely unsuccessful. The Casco class represented an effort to develop a semi-submersible warship, an effort that continued for another half century. But overall, the class was a tremendous failure. The Casco monitors, 225 feet long, had a draft of only six feet, and a freeboard of fifteen inches. They had internal ballast tanks, which could be flooded to lower the ship's silhouette when going into battle to a freeboard of less than three inches, but leaks and seepage of water in the vessels made them nearly useless. Casco was launched May 1864 by Atlantic Works, Boston, Mass. Prononunced unseaworthy when nearly completed, on 25 June 1864 she was ordered to be converted to a torpedo vessel, without turret or heavy guns.

These single-turrent monitors were followed by larger dual-turret monitors. If the Casco had pre-figured 20th Century Submarines, these dual-turret monitors were the fore-runners of the Dreadnaught and other all-big-gun ships of the 20th Century. The USS Milwaukee, was the name ship of class of four 1300-ton double-turret ironclad river monitors on a 229 foot long hull. The USS Onondaga was a 2592-ton twin-turret monitor, on a 226' long hull. The USS Monadnock was the first of a two-ship class of 3295-ton twin-turret monitors which featured a longer hull -- 258'6". And the USS Miantonomoh was the first of a two-ship class of 3400-ton twin-turret monitors, also on a 258'6" long hull.

The USS Roanoke, a 4772-ton steam frigate, was cut down to her gun deck and rebuilt as a triple-turret armored warship. It was originally expected that this work would produce a seagoing ironclad ram in minimal time, but problems with armor supply and fabrication slowed her conversion considerably. Experience quickly and convincingly demonstrated that she was unsuitable for fighting on the opean ocean. Sea trials indicated that her heavy turrets caused her to roll dangerously in a seaway, and that her hull was not sufficiently strong to bear their weight and the concussion of the continuous firing.