Rear Admiral John J. Almy was appointed a midshipman in the Navy in 1829 and served 48 years, 27 years and 10 months at sea (the largest amount of sea service credited to any officer). He was commissioned commander in April 1861, just as the civil war broke out, and was constantly in command during the year along the Atlantic coast. While on this duty, in command of the Connecticut, he captured and sent in four noted blockade-running steamers, laden with valuable cargoes, while he ran ashore and destroyed three others.

Being promoted to a captaincy in 1865, he served until his retirement in 1877. In 1875 King Kalakaua of Hawaii presented him with the order of King Kamehateha I, in recognition of the courtesies shown to the king on the occasion of his visit to the United States.