Most of the Civil War monitors were designed by John Ericsson, and used a turret of his own design. Ericsson's monitors were built with a shoal iron hull supporting an ironclad "raft", the raft being the only portion visible above water. The raft was of very low freeboard, and generally featured a large overhang all around, particularly at the bow and stern. The joining of the iron hull to the overhanging raft was a weak point in most designs.
Most of the surviving ships went into reserve ("ordinary") immediately after the Civil War. Most remained in reserve for many years, generally with little or no additional service, before finally being disposed of.
Concept/Program: The first "monitor", and gave her name to the type. The vessel was intended as a means to counter Confederate ships attempting to challenge the blockade of southern ports; the type also saw considerable service in attacking coastal fortifications. This was the first US warship fitted with a turret.
Design: Designed by Ericsson. Set the standard pattern for all following monitors. In addition to the general weaknesses of the type (i.e. seaworthiness), ventilation was very poor (despite the first use of mechanical ventilation in a warship), leading to terrible conditions for the crew. The originally planned armor had to be much reduced to increase freeboard; even so, freeboard was only 14 inches. The turret mechanism was imprecise and difficult to work. The anchor and hawsepipe were below the "raft", in the hull itself, dangerously close to the water. There was a small pilothouse forward, and low funnels aft. Design speed of 8 knots was not reached. Despite design flaws, this ship set the stage for future monitors and battleships.
Operational: Is best known for her engagement with CSS Virginia (a.k.a. "Merrimac" in Hampton Roads, 9 March 1862; this battle was the first ironclad-vs.-ironclad encounter, and the start of the modern battleship era.
Engaged CSS Virginia 9 March 1862. Participated in actions on the James River and supported Army forces during the summer of 1862. Sank under tow off Cape Hatteras during a Force 7 gale, 31 December 1862.
Concept/Program: An improved version of Monitor, correcting several of the deficiencies of that ship. Most of these vessels were contracted to their designer, John Ericsson, who then subcontracted the actual construction of the ships to various shipyards. Several of these monitors were renamed during 1869, then returned to their original names within a few weeks.
Design: Designed by Ericsson. Compared to Monitor, there was better ventilation, higher funnels, improved "raft" and hull shape, and the pilothouse was atop the turret. Seaworthiness was evidently improved, as Lehigh survived a Force 10 gale off Cape Hatteras, perhaps the worst conditions survived by any ship of this general type. One major weakness was extreme vulnerability to mines.
Variations: Two units were completed with variant armament, as listed above; Lehigh had her 11 inch replaced by an 8 inch Parrot MLR soon after completion.
Modernization: Following the attacks on Charleston there were improvements in armor around the turret and pilothouse bases, turret roof, and decks over magazines and machinery. Two light guns of various types were also fitted in most or all units. All surviving units were eventually fitted with two 15 inch Dahlgren smoothbores.
Operational: Saw extensive service during the Civil War, almost exclusively during the attacks on Charleston, and the blockade of surrounding waters. Postwar they saw little action, but survived to the late 1890's and early 1900's, and were recommissioned for "coast defense" during the Spanish American War.
Departure from Service/Disposal: All the survivors were discarded within a few years of 1900, by which time they were quite old and completely obsolete. Although nominally in reserve, towards the end of their existence (especially after the Spanish-American War), they were probably poorly maintained and in no condition to return to service.
Severely damaged 7 April 1863 during attacks on Charleston; decommissioned at New York for repairs 12 May 1863. During repairs the 8 inch Parrot MLR was apparently replaced by an 11 inch Dahlgren smoothbore. Recommissioned 19 July 1863 and took part in all subsequent actions at Charleston.
Decommissioned to reserve 16 June 1865. Repaired and prepared for service 1876; recommissioned 24 November 1876. Served as a receiving ship at Washington DC 1878-1882, then at the Naval Academy 1883-1892, at Boston 1893-1894. Loaned to the Massachusetts Naval Militia 1895-1896; Georgia Naval Militia 1897-1898.
Recommissioned for Spanish American War service 16 May 1898; decommissioned 11 September 1898. Sold for scrapping 10 October 1899.
Saw extensive service during operations of Charleston. Six alleged accomplices to assassin John Wilkes Booth were briefly imprisoned aboard during April 1865, while Booth's body was also aboard. Decommissioned to reserve mid-late 1865. Sold for scrapping 14 April 1904.
Saw extensive service off Charleston; badly damaged in action 7 April 1863.
Decommissioned to reserve 11 August 1865. Renamed Atlas 15 June 1869, then Nahant 10 August 1869. Recommissioned for Spanish American War service 12 April 1898; decommissioned postwar, probably September 1898. Sold for scrapping 6 April 1904.
Saw extensive service around Charleston. Mined in the Charleston River 16 January 1865 and sank in 15 seconds.
Survived the storm that sank Monitor. Saw extensive service around Charleston; captured CSS Atlanta 17 June 1863. Sunk in a gale off Morris Island, Charleston, 6 December 1863, due to shipping water through the hawsepipe and hatches while at anchor.
Operated in Hampton Roads and area rivers, then off Charleston. Decommissioned to reserve postwar, probably mid-1865. Renamed Jason 15 June 1869. Recommissioned for Spanish American War service 13 May 1898; decommissioned 1899. Sold for scrapping 1905.
Served exclusively in operations around Charleston. Decommissioned to reserve 26 July 1865. Renamed Goliath 15 June 1869, then Catskill 10 August 1869. Repaired and prepared for service at New York Navy Yard 1874-1875; recommissioned late 1875 or early 1876. Decommissioned to reserve late 1877 or early 1878.
Recommissioned for Spanish American War service 26 April 1898; decommissioned 22 September 1898. Sold for scrapping 4 December 1901.
Saw extensive service around Charleston. Decommissioned to reserve 24 June 1865. Renamed Medusa 15 June 1869, then Nantucket 10 August 1869. Briefly recommissioned from 29 July 1882 to 12 December 1882 and again 16 June 1884 to 6 October 1884, returning to reserve when decommissioned.
Loaned to the North Carolina Naval Militia 1895. Apparently recommissioned for Spanish American War service; dates unknown. Sold for scrapping 14 November 1900.
The 11 inch smoothbore was replaced by an 8 inch Parrot MLR immediately after completion. Operated in Hampton Roads and the James River, then off Charleston. Ran aground under enemy fire and was damaged, 16 November 1863.
Decommissioned to reserve 9 June 1865. Recommissioned 15 December 1875 as a training ship for the Naval Academy, then operated off Port Royal. Decommissioned to reserve 1879. Recommissioned for Spanish American War service 18 April 1898; decommissioned 8 September 1898. Sold for scrapping 14 April 1904.
Apparently was completed with two 15 inch Dahlgren smoothbores. Decommissioned to reserve shortly after commissioning. Loaned to the California Naval Militia 1896-1897. Apparently reactivated for Spanish-American War service; dates unknown. Sold for scrapping 22 March 1899.
Concept/Program: An improved version of the Passaic class, taking into account war experience. Four units were incomplete at the end of the Civil War.
Design: Designed by Ericsson. Significant changes from the Passaic design included heavier deck armor, better internal backing for the armor, uniform main batteries, and heavy armor around the turret base. As in the previous classes, they were highly vulnerable to mines. The design speed of 13 knots was not met.
Operated in the James River, then in blockade service, and in attacks on Fort Fisher.
Decommissioned to reserve 30 June 1865. Renamed Scylla 15 June 1869, then Canonicus 10 August 1869. May have been overhauled during 1869-1972. Recommissioned 22 January 1872 and operated with the fleet, but was frequently placed out of commission for short periods. Decommissioned to reserve 1877. Retained in reserve for use as a display at the 1907 Jamestown Exposition; was cleaned up, towed to the Exposition and placed on display, but was not recommissioned or made operable. Sold 19 February 1908.
Saw extensive service in the James River and in the assault on Wilmington. One 15" gun exploded 12 January 1865. Two alleged accomplices to assassin John Wilkes Booth were briefly imprisoned aboard during April 1865.
Decommissioned to reserve 13 June 1865. Recommissioned 30 April 1869 and operated along the Florida coast. Renamed Centaur 15 June 1869, then Saugus 10 August 1869. Decommissioned to reserve 31 December 1870; recommissioned 9 November 1872; decommissioned to reserve 9 March 1874; recommissioned 10 October 1874; decommissioned to reserve 8 October 1877. Condemned 1886, sold for scrapping 25 May 1891.
Operated in the James River, then in the Gulf of Mexico. Mined in Mobile Bay 5 August 1864; capsized and sank in 25-30 seconds.
Operated in the Gulf of Mexico, including attacks on Mobile.
Decommissioned to reserve August 1865. Renamed Neptune 15 June 1869, then Manhattan 10 August 1869. Prepared for service at Philadelphia 1872-1873, recommissioned 19 November 1873. Was inactive after June 1877, but actual date of decommissioning is unknown. Stricken for disposal 14 December 1901; sold for scrapping 24 March 1902.
Participated in the attacks on Charleston and Wilmington, and operated in the James and Appomatox Rivers.
Decommissioned to reserve June 1865; recommissioned 15 January 1866. Renamed Castor 15 June 1869, then Mahopac 10 August 1869. Decommissioned to reserve 11 March 1872; recommissioned 21 November 1873. From 1876 to 1888 she was apparently mostly stationary in various ports. Decommissioned to reserve 1889. Stricken for disposal 14 January 1902; sold for scrapping 25 March 1902.
Operated with the fleet until 1879, then served as station ship at Washington, DC. Decommissioned to reserve 1885. Loaned to the Connecticut state militia 1896. Returned to the Navy and recommissioned for Spanish American War service 30 April 1898; decommissioned 20 September 1898. Sold for scrapping 17 January 1899.
Operated from Key West briefly. Decommissioned at Philadelphia for repairs 1 July 1871, recommissioned 13 January 1874; decommissioned to reserve 27 July 1875. Recommissioned 5 November 1875 but remained inactive; decommissioned to reserve 30 June 1891.
Loaned to the New Jersey Naval Militia 26 September 1895. Returned to the Navy and recommissioned for Spanish American War service 9 July 1898, but decommissioned 1 September 1898, before necessary repairs and overhaul had been completed. Sold for scrapping 10 October 1899.
Concept/Program: A larger purpose-built monitor, essentially the equivalent of two Passaic class ships. In service she saw only riverine duties, but was intended for coastwise duties as well.
Design: Designed by Quintard. Had a conventional iron hull with 14" freeboard. Turrets were essentially identical to those of the Passaic class.
Operational: During the Civil War she served only on the James River.
Saw extensive service along the James River, supporting Army operations.
Decommissioned to reserve 8 June 1865. Sold to her builder 12 July 1867, and was then resold to France under the same name. Was rearmed by the French with four 9.4 inch rifles; remained in service through 1903, stricken 1904, and subsequently scrapped.
Concept/Program: Larger dual-turreted monitors, generally considered the best US monitors of the era. Two ships of the class undertook major ocean voyages, indicating a vast improvement in seaworthiness over the earlier classes.
Design: Designed by the Navy. The hull was of conventional form, but was unfortunately wooden, not iron. Freeboard was 31 inches. The turrets were similar to those of the Passaic class, but slightly larger; a pilothouse was fitted atop each turret. There was a light hurricane deck between the turrets, a tall funnel and a tall ventilation shaft. There were variations among the ships, and some sources identify them as four one-ship classes. Tonawanda's turrets were closer together than in the other three ships.
Departure from Service/Disposal: By the 1870's the wooden hulls were badly rotted, and the ships were disposed of. They were nominally "repaired" as "New Navy" monitors, but in fact the old wooden ships were sold to the shipbuilders as partial payment for the new iron ships, and were scrapped.
Sent to Europe under tow in 1866; operated in European waters 16 June 1866 to 15 May 1867. Decommissioned to reserve 26 July 1867; recommissioned 15 November 1869; decommissioned to reserve 28 July 1870.
Transferred to John Roach, Chester, PA for scrapping, 1874, as partial payment for a new monitor of the same name.
Participated in the assault on Fort Fisher and in operations on the James River. Sent to the Pacific under tow; departed Philadelphia 5 October 1865 and arrived at San Francisco 21 June 1866. Decommissioned to reserve 30 June 1866.
Transferred to Continental Iron Works, Vallejo, CA for scrapping, 1874-75, as partial payment for a new monitor of the same name.
Saw no combat during the Civil War. Decommissioned to reserve 30 September 1865. Renamed Terror 15 June 1869. Recommissioned 27 May 1870; decommissioned to reserve 10 June 1872.
Transferred to William Cramp & Sons, Philadelphia, PA for scrapping, 1874, as partial payment for a new monitor of the same name.
Decommissioned to reserve 22 December 1865. Recommissioned 23 October 1866 as a training ship for the Naval Academy. Renamed Amphitrite 15 June 1869. Apparently decommissioned to reserve 1872.
Transferred to Harlan & Hollingsworth Co., Wilmington, DE for scrapping, 1873-74, as partial payment for a new monitor of the same name.
Concept/Program: A class of shallow-draft dual-turret monitors designed for river service, but also employed in the Gulf of Mexico. Apparently were some of the best-designed monitors of the time, and were generally a success.
Design: Designed by Eads. They were iron-hulled with a turtleback deck. The forward turret was a standard Ericsson turret (as in the Passaic class), but the aft one was designed by Eads. The Eads turret allowed double the elevation of the main guns (20 degrees vs. 10 degrees). There was a pilothouse at deck level, abaft the forward turret. Additional deck armor was later added over the magazines and perhaps over the machinery. Evidently had much better compartmentalization than other monitors of the time, as the one that was mined took three minutes to sink (vs. 15-30 seconds for other classes), and one compartment of the sunken ship did not flood for nearly an hour.
Operated exclusively in the area of Mobile, AL. Mined and sunk in the Blakely River, 29 March 1865. Salvaged in 1868, towed to St. Louis and scrapped; some material reportedly was used in the construction of the Eads Bridge in St. Louis.
Operated on the Mississippi for several months, then saw extensive service around Mobile, AL, and escort and blockade duties in other areas.
Decommissioned to reserve 27 September 1865. Renamed Tornado 16 June 1869, then Winnebago 10 August 1869. Sold 12 September 1874 and subsequently scrapped.
Operated briefly on the Mississippi, then exclusively in the area of Mobile, AL.
Decommissioned to reserve 6 July 1865. Renamed Samson 15 June 1869, then Chickasaw 10 August 1869. Sold 12 September 1874 and converted to a railroad ferry under her original name. Converted to sidewheel propulsion in 1881; renamed Gouldsboro in 1882. Scrapped in 1944.
Operated on the Mississippi for several months, then exclusively in the area of Mobile, AL.
Decommissioned to reserve 29 July 1865. Renamed Cyclops 15 June 1869, then Kewaydin 10 August 1869. Sold 12 September 1874 and subsequently scrapped.
Concept/Program: Designed as shallow-draft coastal monitors; were to be fitted with extra ballast tanks to ballast down and reduce freeboard when entering battle. The design weight calculations were very badly flawed, so the ships were badly overweight and had very little freeboard. When launched, without turret or stores aboard, one of the early ships had 3 inches freeboard. Several ships were, therefore, completed as spar torpedo boats, without turrets and with thinner deck armor; these vessels turned out to be utterly useless in this role, due to low speed. The other vessels were rebuilt with their decks raised, but were generally unsatisfactory. Many were never commissioned, and few saw any significant service. The entire class must be regarded as the least satisfactory warships of their era.
The exact dates on which the conversions and modifications were ordered are not known in most cases. However, based on known dates, it appears that the modifications for the monitors (i.e. raised decks) were ordered on 24 June 1864, and that the spar torpedo boat conversions were ordered the following day.
Design: Was not an Ericsson design, but were generally similar to his designs. The deck was slightly turtle-backed. The hull was so shoal that the blades of the propeller rotated partially above water, and slots were cut in the overhanging deck to accommodate this. In the units completed as torpedo boats there was no turret; the gun was mounted on an exposed pivot mounting, and a spar torpedo was added. Those completed as monitors had their hulls deepened (i.e. decks raised) by approximately 22 inches to restore buoyancy; this allowed the design weights to be carried, but the ships still were not satisfactory. All but Tunxis had this change made prior to commissioning.
Variations: There appear to have been considerable variations in the dimensions and weights of the hulls, probably because they were hurriedly constructed by many different builders, perhaps with incomplete plans. Tunxis, for example, was much lighter than most, and was able to float, fully armored and armed with 1x11 inch Dahlgren and 1x8 inch Parrot MLR, prior to having her hull deepened.
Departure from Service/Disposal: All were laid up in reserve ("in ordinary") promptly after the Civil War, and all were sold for breaking up in 1874-1875, many without ever having been commissioned.
Served in the James River, clearing mines, then in the Potomac. Decommissioned to reserve 10 June 1865. Renamed Hero 16 June 1869. Scrapped at Washington Navy Yard April 1875.
Was the only ship of this class completed to the original design. Found to be unseaworthy during her first ocean voyage, 21 September 1864, and was promptly decommissioned pending modifications. Hull deepened at William Cramp & Sons, Philadelphia, starting 19 October 1864; was rearmed with two 11 inch smoothbore during the rebuilding. Recommissioned 12 July 1866, but was immediately decommissioned to reserve.
Renamed Hydra 15 June 1869, then Ostego 10 August 1869. Sold and scrapped 1874.
Saw very limited service, mostly as a station ship. Decommissioned to reserve 24 June 1865. Renamed Orion 15 June 1869, then Piscataqua 10 August 1869. Sold 1874 and subsequently scrapped.
Saw no active service. Decommissioned to reserve 27 June 1865. Renamed Gorgon 15 June 1869, then Minnetonka 10 August 1869. Transferred to Harlan & Hollingsworth & Co., Wilmington, DE for scrapping, 1875, as partial payment for construction of a new monitor by that yard.
Saw limited service around Charleston post-war. Decommissioned to reserve 26 May 1866. Renamed Erebus 15 June 1869, then Algoma 10 August 1869. Scrapped at League Island, Philadelphia, 1874.
Saw no active service. Decommissioned to reserve 24 August 1865. Renamed Aetna 16 June 1869, then Nausett 10 August 1869. Transferred to John Roach, Chester, PA for scrapping, August 1875, as partial payment for construction of two new monitors by that yard; scrapped by Roach at New York.
In design terms, these craft (except the converted Roanoke) were generally similar to the smaller coastal monitors, but were greatly enlarged and refined in the details to improve open-ocean performance. They were also significantly faster than most of the smaller ships. However, they never had a chance to prove themselves, as only two ships were completed, and neither saw combat.
Concept/Program: One of the largest monitors of the Civil War era, and the only one to mount three turrets. Was converted from the steam frigate Roanoke; prior to conversion the ship was sister to USS Merrimack (later CSS Virginia). Although not usually considered as a seagoing ship, she was intended as the first seagoing monitor in US service, but design flaws prevented her employment in this role. Was not a success.
Design: Was not an Ericsson design. The wooden frigate was razeed (cut down) and the remaining freeboard armored; three turrets were fitted. A fourth turret had been planned, but the weight could not be accommodated. Pilothouses were fitted on two turrets; there was a tall funnel, and possibly a hurricane deck, but no other superstructure. The armament was oddly distributed, but in total amounted to two each 15 inch Dahlgrens, 11 inch Dahlgrens, and 8 inch Parrots. The wooden hull was too weak for the weight of the armor and turrets, and the stern was damaged when the ship was re-launched. She had high freeboard (for a monitor), but rolled heavily and was generally unseaworthy.
Operational: Due to her unseaworthiness, she was confined to harbor defense duties at Hampton Roads, and saw no action.
Served as a harbor defense ship at Norfolk. Decommissioned to reserve 20 June 1865. Recommissioned to commissioned reserve 13 January 1874; decommissioned to reserve 12 June 1875. Transferred to John Roach, Chester, PA for scrapping, 1876, as partial payment for construction of a new monitor by that yard, but approval for scrapping was revoked and the ship remained at the Roach shipyard, nominally in reserve. Stricken for disposal 5 August 1882, sold 27 September 1883 and scrapped at Chester, PA.
Concept/Program: The first purpose-built US monitor intended to be truly seagoing; was designed as a "seagoing high speed monitor". Although her speed and seaworthiness were an improvement over previous ships, the design had problems, and she left much to be desired.
Design: A single-turret Ericsson design, generally increased in size over the coastal ships, with the lines of the raft improved, and with less overhang. There was a tall funnel and tall ventilation shaft; there probably was a light hurricane deck amidships. Design speed was 15 knots, but this was not reached. The design was overweight, reducing freeboard to 16 inches. The main shaft bearings were too short, resulting in excessive wear.
Was sent to participate in the assault on Fort Fisher, but had to return to port due to excessive wear on the shaft bearings. Decommissioned to reserve 5 September 1865.
Recommissioned 12 January 1874. Decommissioned for disposal 1 June 1877; hulk remained at League Island, Philadelphia, until sold for scrapping 27 September 1883.
Concept/Program: Intended as a "seagoing high speed monitor". Ultimately would have been an enlarged version of Dictator, carrying the largest diameter guns ever fitted in a ship. The ship went through a complete redesign prior to construction, and was never completed. The ship was nominally "repaired" as a "New Navy" monitor, but in fact was sold to the shipbuilder as partial payment for a new ship, and was scrapped.
Design: A compromise design between Ericsson and the Navy. The original design was for a dual turreted ship with four 10 inch Dahlgren smoothbores, but this was altered to the single turreted design listed above. Ericsson favored a single turret and single shaft; the Navy wanted dual turrets and dual shafts. There were problems in producing the 20 inch guns, and only one was ever cast. Design speed was 15 knots, but it is believed that horsepower and speed would have been similar to Dictator.
Concept/Program: The largest monitors ordered during the Civil War. Would have been far more seaworthy than any of the previous classes. Were incomplete at the end of the Civil War but were improperly preserved and protected while awaiting a decision on future completion; ultimately had to be scrapped after their timbers became rotten.
Design: A Navy design. Essentially an enlarged version of the Miantonomoh class, with improved lines. Freeboard was projected to be 45 inches. The turrets would have been as in Dictator. The hull was wooden with iron structure to support the turrets. There would have been pilothouses on the turrets, a hurricane deck, two tall funnels, and a tall ventilation shaft.
