Unadilla - class gunboat The " Unadilla " class was a class of gunboat built for the Union Navy at the outbreak of the American Civil War . Ships of the class were also known as " 90 - day gunboats " due to their rapid construction . The class was designed to be fully oceangoing while having a light enough draft to be able to operate close inshore , for blockade duty or other operations in shallow waters . " Unadilla " - class gunboats took part in many coastal and river operations , most notably as the bulk of the fleet which captured the vital Confederate port of New Orleans in April 1862 . As blockade ships , the 23 vessels of the class captured or destroyed no fewer than 146 enemy blockade runner s during the war — about 10 percent of the total number of Confederate blockade runners so neutralized . The " Unadilla " class was sold off quickly by the Navy at the end of the war , most of them going into merchant service . Little is known about their subsequent careers . Construction and design . Development . With the outbreak of the American Civil War in April 1861 , the U . S . Navy was faced with an urgent need for light - draft gunboats able to operate both at sea and close inshore to help enforce the Union blockade of Confederate ports . Since the Navy ' s Chief Engineer , Benjamin F . Isherwood , had recently designed and overseen construction at the Novelty Iron Works in New York of the engines for two similar gunboats , built for the Imperial Russian Navy , he had to hand a ready - made design suitable for the new U . S . Navy gunboats , which was accepted by Secretary of the Navy Gideon Welles . The two men agreed , as a time - saving measure , to award the first four engine contracts directly to the Novelty Works , dispensing with the usual tendering process ; in the event the contracts for all 23 vessels of the class would be signed between 29 June and 10 July without Congressional approval . As a result , the first four vessels of the new " Unadilla " class were completed in the remarkably short time of about three months , earning the class as a whole the popular name " 90 - day gunboats " . Contract distribution and cost . All ships of the class were built in privately owned shipyards along the Eastern seaboard . Six contracts went to New York shipbuilders , five to the State of Maine , four to Massachusetts , three each to Connecticut and Philadelphia , Pennsylvania , and one each to Delaware and Maryland . No individual shipyard built more than one ship . By contrast , reflecting the relative strength of the States ' industrial bases , more than half the machinery contracts went to New York - based companies — seven to the Novelty Works , three to the Morgan Iron Works and two to the Allaire Works — while Pennsylvania companies accounted for another four , Massachusetts for three , Connecticut two and Delaware and Maryland one each . Overall cost of the individual ships varied between $ 90 , 000 and $ 103 , 500 , with cost of the hulls varying between $ 52 , 000 and $ 58 , 500 . The largest price differential was for the machinery contracts , the first four of which , with the Novelty Works , were for only $ 31 , 500 , as opposed to the $ 42 , 000 to $ 46 , 500 for the later ships . The difference is probably due primarily to the fact that the later vessels had 60 % more boiler power than the original four . Total cost of all 23 vessels was $ 2 , 170 , 000 . Hulls . The hulls of the " Unadilla " - class gunboats were designed by Samuel H . Pook , under the direction of the Navy ' s Chief of the Bureau of Construction , Equipment and Repairs , John Lenthall . The design was possibly based on the 1860 rebuild of , designed by Pook ' s father Samuel M . Pook . The hulls were in length on the waterline , with a beam of , hold depth of and draft of . Some details of the six New York - built vessels are available . These ships had frames , keels and keelson s of white oak " of the best quality " , with port stanchion s of locust and live oak . The keels and keelsons were fastened with corrosion - resistant copper bolts . The hulls were strengthened with diagonal iron braces , secured amidships " at the turn of the bilge " and running upward at a 45° angle to the outer frames . The ship stem s were also strengthened with iron strapping . According to some sources , ships of the class were built with unseasoned timber and would therefore have been expected to have short working lives . Machinery . The ships of the " Unadilla " class were each powered by a pair of bore , stroke horizontal back - acting engines , driving a single screw propeller . As with the hulls , additional details for the machinery of the six New York - built ships are available ; the machinery of the others was similar if not identical . The New York - built ships had two boilers each , of the Martin ' s vertical tubular type , placed side by side and spaced six inches apart . The boilers , " made of the best quality American charcoal iron " , were 12 ft 3 in long , 8 ft 3 in wide and 9 ft 3 in high , with two furnaces each . The boilers were safety tested to a pressure of 60 psi before installation . The engines were fitted with Sewell ' s patent surface condensers . The ships ' propellers were four - bladed , and nine feet in diameter with a mean blade pitch of 12 feet 6 inches . Sources vary as to the speed of the ships . Some give a speed of 10 knots , but 8 to 9 knots seems to have been the typical speed during the war . Recorded speeds vary all the way from 6 knots to 11 . 5 knots . In all likelihood , the performance of the vessels was less than ideal in wartime conditions due to infrequency of maintenance , particularly for the boilers . Launch and commission . The first vessel of the class , " Unadilla " , was launched on 17 August 1861 , barely two months after the signing of the contract . The rest rapidly followed , with another three being launched in August , four in September , fourteen in October and the last one , " Penobscot " , in November . " Unadilla " was again first to be commissioned , on 30 September , just 93 days after the laying of her keel . A total of eleven were commissioned before the end of the year , and another eleven by February 1862 . " Marblehead " was the last ship of the class to enter commission , on 8 March . Though popularly known as the " 90 - day gunboats " then , only the first four vessels of the class were commissioned in anything like 90 days . The rest took an average of about three months just to launch . Overall , the ships averaged a little under six months from signing of the contract to commission . Armament and complement . Vessels of the class were initially armed with one Dahlgren smoothbore cannon ; two 24 - pounder smoothbores and a single 20 - pounder Parrott rifle . As the war continued , most of them were upgunned on an " ad hoc " basis , so that they ended up with a variety of different armaments . The crew complement is listed in some recent sources as 114 officers and men ; however , " DANFS " and other sources give varying figures for the individual ships , ranging from a complement of 65 ( " Sciota " ) to 94 ( " Aroostook " ) , with an average per ship of 80 . The reason for these apparent discrepancies is unknown . Performance . Sources vary as to the performance of the " Unadilla " class . According to Bauer and Roberts , the ships " sailed well in a strong wind and handled easily but rolled badly . " Gardiner is less generous , describing the vessels as " poor sailors ; their machinery frequently broke down ; the steering mechanism was inefficient ; and they were slow ; maximum speed being 8 – 9 knots . " Thomas Main , a well - known contemporary engineer , criticized the engines of the class as " unusually heavy in all their parts " , a common criticism of Isherwood ' s engines by private contractors . According to Main , the engines were fully 2 . 78 times heavier than required , leading to reduced efficiency and performance . Main notes that with a speed of only around 9 knots , the vessels were incapable of catching the faster blockade runners with speeds of 12 to 14 knots . Whatever their shortcomings , gunboats of the class were nonetheless to accumulate an " impressive " record of service during the war . Service history . Though the main task of the " Unadilla " class was simply to enforce the blockade of Confederate ports in line with the Anaconda Plan , many ships of the class also participated in related operations against Confederate forts and population centers along the Southern coastline and its rivers . These operations included shore raids and invasions , bombardments , and engagements with enemy land or naval forces . Battle of Port Royal . The first major such operation involving ships of the class occurred after the U . S . Navy determined that a supply port deep in Confederate territory would be required in order to effectively enforce the blockade of the Confederate coastline . In late October 1861 , a large fleet of 77 ships , including 19 warships — the largest fleet then assembled by the Navy — departed New York with the capture of Port Royal , South Carolina as its objective . On 4 November , four gunboats of the fleet , including the " Unadilla " - class vessels , and , provided protection for the survey vessel as the latter made soundings in Port Royal harbor . The following morning , the same three " Unadilla " - class ships and two other gunboats returned to the harbor to engage the Confederate forts and gauge their strength . On 7 November , the entire Naval battle fleet , including the three previously mentioned " Unadilla " - class vessels along with a fourth , USS " Unadilla " , engaged and defeated the two enemy forts , thus capturing the harbor . Port Royal would subsequently become a key supply port for the Union cause . Capture of New Orleans . The largest and most important contribution made by ships of the " Unadilla " class to a single operation was to the capture of New Orleans , the Confederacy ' s largest and most economically powerful city , in April 1862 . For the operation , Captain David Farragut , Commander of the West Gulf Blockading Squadron , assembled a fleet of 17 warships including nine " Unadilla " - class gunboats : , , , , , , , and . On the night of April 20 , Farragut despatched three of his " Unadilla " - class gunboats , " Itasca " , " Kineo " and " Pinola " to remove the chains obstructing the Mississippi River below New Orleans . Though coming under heavy but inaccurate fire from Forts Jackson and St . Philip , the vessels were able to clear a narrow passage . On the night of the 24th , Farragut took the bulk of his fleet through the passage , though three of his " Unadilla " - class gunboats , " Itasca " , " Kennebec " and " Winona " , became entangled in the river obstructions and were forced to turn back . The rest of the fleet , however , continued on to New Orleans , which was forced to capitulate a few days later . Vicksburg campaign . The capture of New Orleans enabled Naval forces to move further north along the Mississippi to threaten the key Confederate city of Vicksburg . Several ships of the class were subsequently involved in the ensuing Vicksburg Campaign . For example , in June 1862 , several vessels of the class were involved in the " run past Vicksburg " to link up with the naval forces of the upper Mississippi , although this action proved to be of little significance . In August , " Cayuga " , " Katahdin " , " Kineo " and " Sciota " were involved in the Battle of Baton Rouge , and " Katahdin " and " Winona " in the recapture of the city in December . Vicksburg was however far too well defended to be threatened by the Navy , and defeat of the Confederate forces in this theater of operations was ultimately left to the Army . Other actions . The " Unadilla " class was involved in numerous other operations against enemy - held territory during the war , most notably the Battle of Mobile Bay in August 1864 and the First and Second battles of Fort Fisher in December 1864 and January 1865 respectively . The main duty of the class , however , was maintenance of the blockade along the Confederate coast . While vessels of the class were too slow to catch the faster blockade runners , they nonetheless accumulated an impressive record of prizes during the war , capturing or destroying no less than 146 blockade runners during the war — almost 10 % of the total number of blockade runners neutralized by the Union blockade . The most successful of the " Unadilla " s in this regard were , with 21 prizes ; " Kanawha " with 19 ; and with 13 each ; and and with 11 apiece . Only one ship of the class , " Sciota " , was sunk during the war , but ironically this vessel was sunk on two separate occasions . The first occurred on 14 July 1863 when collided with " Sciota " on the Mississippi , sinking the latter in about 12 feet of water . " Sciota " was raised and returned to service , but shortly after the war , on 14 July 1865 — the day of Lincoln ' s assassination — " Sciota " ran onto a mine in Mobile Bay and was sunk a second time . Again she was salvaged , but this time only to be sold out of the Navy . Postwar service . After the war , most of the ships of the " Unadilla " - class were quickly decommissioned and sold into merchant service . Seventeen had been decommissioned by August 1865 , and fifteen of these had been sold by the end of the year , with the remaining two , " Seneca " and " Penobscot " , seeing no further naval service and being sold in 1868 and 1869 respectively . Some of these vessels were still in existence as late as 1885 . Of the remaining six , " Chocura " and " Tahoma " briefly saw service with the Gulf Squadron in 1866 - 67 before being decommissioned and sold in the latter half of 1867 ; " Marblehead " saw service with the North Atlantic Squadron , and " Huron " in South American waters , until their decommission in late 1868 and subsequent sale . The last two vessels of the class to see service with the Navy , and " Unadilla " , were transferred to the newly established Asiatic Squadron in 1867 and subsequently employed in the suppression of piracy along the coast of China . In June 1868 , " Unadilla " became the first American warship to enter Siam ' s Chao Phraya River , bearing gifts from the President of the United States , Andrew Johnson , to Chulalongkorn , King of Siam . In 1869 , both " Aroostook " and " Unadilla " were condemned as unfit for further service due to rotting hulls — a legacy of their construction with unseasoned timber — and they were sold shortly thereafter . " Unadilla " became the merchant " Dang Wee " and was sunk in a collision off Hong Kong in the fall of 1870 ; " Aroostook " s later history , like that of most other vessels of the class , is unknown . List of ships .