Union Navy The Union Navy is the label applied to the United States Navy ( USN ) during the American Civil War , to contrast it from its direct opponent , the Confederate States Navy ( CSN ) . The term is sometimes used carelessly to include vessels of war used on the rivers of the interior while they were actually under the control of the United States Army , referred to in the same fashion as the Union Army . Primary missions . The primary missions of the Union Navy were : Transformation . To accomplish these , the Union Navy had to undergo a profound transformation , both technical and institutional . During the war , sailing vessels were completely supplanted by ships propelled by steam for purposes of combat . Vessels of widely differing character were built from the keel up in response to peculiar problems they would encounter . Wooden hulls were at first protected by armor plating , and soon were replaced by iron or steel throughout . Guns were reduced in number , but increased in size and range ; the reduction in number was partially compensated by mounting the guns in rotating turrets that could fire in any direction . The institutional changes that were introduced during the war were equally significant . The Bureau of Steam Engineering was added to the bureau system , testimony to the Navy ' s conversion from sail to steam . Most important from the standpoint of Army - Navy cooperation in joint operations , the set of officer ranks was redefined so that each rank in the Army had its equivalent in the Navy . The establishment of the ranks of admirals implied also a change of naval doctrine , from one favoring single - ship operations to that of employing whole fleets . The ships . At the start of the war , the Union Navy had 42 ships in commission . Another 48 were laid up and listed as available for service as soon as crews could be assembled and trained , but few were appropriate for the task at hand . Most were sailing vessels , some were hopelessly outdated , and one ( ) served on Lake Erie and could not be moved to the ocean . During the course of the war , the number in commission was increased by more than a factor 15 , so that at the end the Navy had 671 vessels . Even more significant than the increase in raw numbers was the variety of ship types that were represented , some of forms that had not been seen previously in naval war anywhere . The nature of the conflict , much of which took place in the interior of the continent or in rather shallow harbors along the coast , meant that vessels designed for use on the open seas were less useful than more specialized ships . To confront the forms of combat that actually came about , the federal government developed a new type of warship , the monitor , based on the original , USS " Monitor " . The Navy took over a class of armored river gunboats created for the Army , but designed by naval personnel , the Eads gunboats . So - called double - enders were produced to maneuver in the confined waters of the rivers and harbors . The Union Navy experimented with submarines before the Confederacy produced its famed CSS " Hunley " ; the result , USS " Alligator " failed primarily because of lack of suitable targets . Building on Confederate designs , the Union Navy produced and used torpedo boats , small vessels that mounted spar torpedoes and were forerunners of both the modern torpedo and destroyer type of warship . Because of haste in their design and construction , most of the vessels taken into the Navy in this period of rapid expansion incorporated flaws that would make them unsuitable for use in a permanent system of defense . Accordingly , at the end of the war , most of them were soon stricken from the service rather than being mothballed . The number of ships at sea fell back to its prewar level . In total , the Union Navy had 84 , 415 personnel . The Union Navy suffered 6 , 233 total casualties with 4 , 523 deaths from all causes , 2 , 112 Union Sailors were killed by enemy action and 2 , 411 died by disease or injury . The Union Navy suffered 1 , 710 personnel wounded in action , injured , or disabled by disease . The institution . The highest rank available to an American naval officer when the war began was that of captain . ( The Confederate constitution provided for the rank of admiral , but it was to be awarded for valor in battle . No Confederate officer was made admiral until Franklin Buchanan was named such after the Battle of Hampton Roads . ) This created problems when many ships had to operate together , with no clearly established chain of command . Even worse , when the Navy worked with the Army in joint operations , the customary rank equivalency between the two services meant that the naval captain , equivalent to an army colonel , would always be inferior to every army general present . After the existing arrangement had been used for the first year of the war , the case was made that the interests of the nation would be better served by organizing the Navy along lines more like that of the Royal Navy of Great Britain . A set of officer ranks was established in the summer of 1862 that precisely matched the set of Army ranks . The most visible change was that henceforth some individuals would be designated commodore , rear admiral , vice admiral , and finally admiral , all new formal ranks , and equivalent to , respectively , brigadier general , major general , lieutenant general , and general . A doctrinal shift took place at the same time . Prior to the war , the United States Navy emphasized single - ship operations , but the nature of the conflict soon made use of whole fleets necessary . Already at the Battle of Port Royal ( 7 November 1861 ) , 77 vessels , including 19 warships , were employed . This was the largest naval expedition that had ever sailed under the American flag , but the record did not stand for long . Subsequent operations at New Orleans , Mobile , and several positions in the interior confirmed the importance of large fleets in modern naval operations . The system of naval bureaus was revised in the summer of 1862 . Some of the older bureaus were rearranged or had their names altered . The most radical change was the creation of the Bureau of Steam Engineering . Its existence was testimony to the fact that the U . S . Navy would no longer rely upon the winds to propel its ships . More was involved in this decision than meets the eye , as the necessity of maintaining coaling stations around the globe meant that the nation had to rethink its attitude toward colonialism . The blockade . The blockade of all ports in the seceded states was proclaimed by President Abraham Lincoln on 19 April 1861 , one of the first acts of his administration following the bombardment of Fort Sumter . It existed mostly on paper in the early days of the conflict , but became increasingly tighter as it continued . Although the blockade was never perfect , it contributed to the isolation of the South and hastened the devaluation of its currency . For administration of the blockade , the Navy was divided into four squadrons : the North Atlantic , South Atlantic , East Gulf , and West Gulf Blockading Squadron s . ( A fifth squadron , the Mississippi River Squadron , was created in late 1862 to operate in the Vicksburg campaign and its consequences ; it was not involved with the blockade . ) Invasion . Two early invasions of the South were meant primarily to improve the blockade , and then led to further actions . Following the capture of Cape Hatteras , much of eastern North Carolina was soon occupied by the Union Army . The easy success in North Carolina was not repeated after the seizure of Port Royal in South Carolina , as determined resistance prevented significant expansion of the beachhead there . Charleston did not fall until the last days of the war . The later capture of Fernandina , Florida was intended from the start to provide a southern anchor for the Atlantic blockade . It led to the capture of Jacksonville and the southern sounds of Georgia , but this was not part of a larger scheme of conquest . It reflected mostly a decision by the Confederate government to retire from the coast , with the exception of a few major ports . Late in the war , Mobile Bay was taken by fleet action , but there was no immediate attempt to take Mobile itself . The capture of New Orleans was only marginally connected with the blockade , as New Orleans was already pretty well sealed off . It was important , however , for several other reasons . The passage of the forts below the city by Farragut ' s fleet showed that fixed fortifications could not defend against a fleet that was powered by steam , so it was crucial for the emergence of the Navy as equal to the Army in national defense . It also demonstrated the possibility of attacking the Confederacy along the line of the Mississippi River , and thus was an important , even vital , predecessor of the campaign that ultimately split the Confederacy . Finally , it cast doubt on the ability of the Confederacy to defend itself , and thus gave European nations reason not to grant diplomatic recognition . The final important naval action of the war was the second assault on Fort Fisher , at the mouth of the Cape Fear River in North Carolina . It was one of the few actions of the war on the coast in which the Army and Navy cooperated fully . The capture of the fort sealed off Wilmington , the last Confederate port to remain open . The death of the Confederacy followed in a little more than three months . The battles . Inland Waters . Not included in this list are several incidents in which the Navy took part more or less incidentally . These include Shiloh and Malvern Hill . They are not put on the list because naval personnel were not involved in planning or preparation for the battle .