It might come as a surprise to learn that there was no such thing as an Admiral in the United States Navy for nearly ninety years after the Continental Congress established a Navy in October, 1775. One of the reasons for the hesitation to create such a rank was that it seemed to be too much of a nod to the British Royal Navy. But this was far from a consensus view. John Paul Jones, for one, advocated for the rank because he saw the need for an authority above Captains—the highest authorized rank at the time—to settle disputes that might arise between them. And there were some Secretaries of the Navy who, rather than seeking to create a Navy with a structure distinct from that of other nations, wished to have the rank introduced because it was used in other Navies.
Until 1857, the highest rank in the U.S. Navy was Captain. But the creation of temporary rank of Flag Officer that year was the stepping stone to the eventual permanent establishment of ranks above Captain. Flag Officers were Captains who senior Navy Captains who, in addition to commanding their own ship, were given control of a squadron of ships. The term Flag Officer is still in use today, and in the Navy it refers to an officer with the rank of Admiral, Vice Admiral, Rear Admiral, or Rear Admiral (lower half) assigned to a station for a two-year period.
In 1862, doubtless in response to the rapid expansion of the U.S. Navy to carry out the blockade of Southern ports and conduct riverine warfare, Congress created the first rank of Admiral, namely Rear Admiral, and appointed nine Captains to the position. Simultaneously, it established the rank of Commodore, which to that time had been a rather vague title. Commodore last much of its prestige when the heads of several Naval Bureaus (Medicine and Surgery, Provisions and Clothing, etc.) were given the rank of Commdore; in 1899 the rank was disestablished, and all Commodores were made rear admirals.
Two years after Congress named the nine Rear Admirals, renowned David Farragut of “Damn the torpedoes!” fame was promoted to Vice Admiral and, in 1866, was named the Navy’s first full Admiral.