One salty bluejacket
“Union Sailor with Remington Root sidehammer revolver” contributed by Ryan M. Cooper Nautical Antiques, Yarmouth Port, Maine, 2011, to the LOC.
The young bluejacket, whose name has been lost to time, witnessed the largest Naval expansion in the young nation’s history, prior to the Great War.
Beginning the conflict with just 42 ships in commission and another 48 in ordinary or on the builder’s ways, by the end of the war there were an amazing 671 under flag, although it should be noted that many of these were no more than armed coasters for blockade duty or small riverine vessels that could never venture offshore. While the 1865 Royal Navy was still king of the high seas, it could be argued that the USN was very much a contender to the throne at the time.
When South Carolina left the Union in Dec. 1860, the Navy had some 1,200 officers from midshipman on up and some 7,600 ratings organized under the 23rd SECNAV Isaac Toucey, a Connecticut lawyer and former senator with no prior military service. Over the course of the war, this would swell to a peak of 84,415 personnel of all ranks, to include an estimated 10,000 African-American Sailors– itself a larger force than the peacetime Navy alone.
The service during the conflict was headed by a man referred to interchangeably as “Poseidon” and “Father Neptune” (the latter by Lincoln), the 24th SECNAV, the formidable white-bearded Gideon Welles. He took over from Toucey in 1861 and at least had the prior experience of a military education (from Norwich) and having previously headed a bureau of the Navy for five years in the 1840s, back in the days when there was no CNO and bureau chiefs basically ran the service.
It did not come without a price. The Union Navy suffered 6,233 total casualties during the Civil War, including 4,523 deaths from all causes, a figure over half its pre-war size.

Regarding the casualty figures: I read that, up until the Civil War, more U.S. Navy officers were killed in duels than in combat.
They were a prickly bunch.