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Ship nomenclature and Ship types

Related Resources:

ONI Official Definitions (1919):
General Order No. 541 (1920):
Classifications of Naval Ships and Craft, SECNAVINST 5030.1E (1968):
Classifications of Naval Ships and Craft, SECNAVINST 5030.1L (1993):
Classifications of Naval Ships and Craft, SECNAVINST 5030.8 (2006):


Ship Nomenclature

The first entry in the statistics line in an individual Dictionary of American Naval Fighting Ships' entry is the nomenclature of the ship when first commissioned. Although now indicated by a combination of two or more letters followed by a number (DDG-51, for example), the reader will note that older ships have the ship type spelled out and sometimes include an associated number (example, ship-of-the-line or Battleship No.12). The dividing line between the two is 17 July 1920, when the Secretary of the Navy approved General Order No. 541, establishing an alpha-numeric designation system.

Until 1920 the nomenclature of a U.S. Navy ship was spelled out (e.g., frigate, sloop-of-war, monitor, torpedo boat, submarine, etc.). Early in the 20th-century, as ship types diversified and became more numerous, the Navy began referring to ships of certain types by a consecutive number indicating the relative order of their construction, applying numbers retroactively back to the beginning of the particular type in question. For instance, the first U.S. destroyer, Bainbridge, was given the number “one” (No.1). Battleships, submarines and torpedo boats were likewise referred to by number, as were some cruisers and monitors. Thus, Pittsburgh was known as Armored Cruiser No. 4; Tonopah as Monitor No. 8; Flusser as Torpedo Boat-Destroyer No. 20; and F-4 as Submarine Torpedo Boat No. 28. In a variation to this practice, register numbers prefixed with the letters "SP" were given to many of the privately owned ships taken into the Navy in World War I. Assigned at the time a ship was inspected and accepted by the Navy, the number bore no relation to the type nomenclature system, but was for identification only.

Following World War I, and the confusion experienced in mailing correspondence and shipping spare parts to ships during the war, Acting Secretary of the Navy Robert E. Coontz approved a standardized system of alpha-numeric symbols to identify ship types (e.g., BB for battleship, DD for destroyer, DM for light mine layer, AD for destroyer tender). Linked with a consecutive number, the use of which now became general for all types of naval ships, these classification symbols provided positive and individual identification of both named and unnamed ships, many of which might not be readily identifiable by name alone.

As with any retroactively applied system, peculiarities and seeming discrepancies were bound to (and still do) appear. George Washington (SSBN-598), for example, was a fleet ballistic missile submarine, nuclear propulsion, with a hull number of 598. This seems to indicate that George Washington was the 598th ballistic missile submarine accepted by the Navy, a reasonable assumption given the mid-20th century practice of using consecutive numbers. This is not the case, however, as the numbers were consecutive by general type, not individual class variations. Thus, SSBNs were slotted into the “submarine” category along with every other variation in submarine type (SS, SSK, SSG, SSN, etc.). George Washington, therefore, received number 598 even though it was actually the first SSBN in the U.S. Navy. Indeed, that submarine was not even the 598th boat accepted by the Navy, as submarine G-1 (ex-Seal) was assigned the hull number 191/2 to fit it into it's proper place in the chronological listing of submarines. This happened in other cases as well, with second-class battleships Texas and Maine, both originally rated as "armored cruisers," preceding Indiana (Battleship No. 1, later redesignated BB-1). In addition, some hull numbers were assigned only to have the ship contract canceled. The slots remained empty so as not to give lower hull numbers to younger ships.

Significantly, the U.S. Navy later altered the tradition of consecutive numbering with the launching of some new or converted classes of ships in the 1950s and beyond, though this initially began during World War II with the Alaska-class (CB-1) battle cruisers. For example, light cruisers converted to guided-missile cruisers gave up their CL numbers, with CL-92 becoming CLG-4; the first nuclear-powered cruiser Long Beach was assigned CGN-9 rather than CGN-160 (the next available cruiser number); and the first Oliver Hazard Perry-class frigate received FFG-7 vice FF-1097. The latest changes took place in the 1990s, with the construction of the Seawolf-class SSN-21 boats and work on an experimental DD-21 class of destroyers. This despite having used SS-21 in 1912 and DD-21 in 1898. The peculiarity in hull numbering apparently came about when the project titles were applied as hull numbers, thus, for example, the “Submarine for the 21st Century” became SSN-21.

Ship Types

The Navy also organized ships by type, both for administrative reasons and to have a system in place to make comparisons with foreign navies, as illustrated by the 1919 Office of Naval Intelligence list of definitions. That general delineation was expanded and broken down into individual ship types with the issue of General Order 541 of 17 July 1920, which established the letter-symbol system of ship designation in use today. Designations are grouped within each category by alphabetically arranged letter symbol.

Since type names and designation symbols are subject to change over the years, as the Navy changed in size, structure and composition. SECNAV 5030.1E from 1968, version L from 1993 and SECNAVINST 5030.8 from 2006 illustrate this evolutionary process.

Ship types are listed under the general type categories (Cruisers, Mine Warfare Types, etc.) as they were or are officially assigned. When the letter-symbol system was first established it was intended that the first letter of a symbol should indicate the type category; as, B for Battleships, A for Auxiliary ships, and so on, with the second letter sometimes, but not always, indicating the sub-class. Since the letter-symbol system began in 1920, many exceptions to this principle have arisen. Ships with a letter prefix denoting one category are sometimes assigned to another while retaining the original symbol. Or a new type category will be setup, with types assigned to it from other categories; these types will sometimes retain their old symbols. For example, the category of Mine Vessels, established in 1928, was assigned ships with symbols beginning with A, C, and D; it was not until the 1950's that most minecraft received new symbols prefixed with M. Amphibious warfare types were considered Auxiliary Ships until 1942, when the prefix L was applied to landing ships and craft; but several amphibious types such as the AKA and APA continued to bear the Auxiliary (A) prefix.


 Dr. Timothy L. Francis, 10 August 2007