Editing Hull classification symbol (section)

== History ==

=== United States Navy ===
The U.S. Navy began to assign unique [[Naval Registry Identification Number]]s to its ships in the 1890s. The system was a simple one in which each ship received a number which was appended to its ship type, fully spelled out, and added parenthetically after the ship's name when deemed necessary to avoid confusion between ships. Under this system, for example, the [[battleship]] [[USS Indiana (BB-1)|''Indiana'']] was USS ''Indiana'' (Battleship No. 1), the [[cruiser]] [[USS Olympia (C-6)|''Olympia'']] was USS ''Olympia'' (Cruiser No. 6), and so on. Beginning in 1907, some ships also were referred to alternatively by single-letter or three-letter codes—for example, USS ''Indiana'' (Battleship No. 1) could be referred to as USS ''Indiana'' (B-1) and USS ''Olympia'' (Cruiser No. 6) could also be referred to as USS ''Olympia'' (C-6), while USS ''Pennsylvania'' (Armored Cruiser No. 4) could be referred to as USS ''Pennsylvania'' (ACR-4). However, rather than replacing it, these codes coexisted and were used interchangeably with the older system until the modern system was instituted on 17 July 1920.<ref name=DerDigiCru1/>

During [[World War I]], the U.S. Navy acquired large numbers of privately owned and commercial ships and craft for use as [[patrol vessel]]s, [[Minelayer|mine warfare vessels]], and various types of naval [[auxiliary ship]]s, some of them with identical names. To keep track of them all, the Navy assigned unique identifying numbers to them. Those deemed appropriate for patrol work received [[section patrol]] numbers (SP), while those intended for other purposes received "identification numbers", generally abbreviated "Id. No." or "ID;" some ships and craft changed from an SP to an ID number or vice versa during their careers, without their unique numbers themselves changing, and some ships and craft assigned numbers in anticipation of naval service were never acquired by the Navy. The SP/ID numbering sequence was unified and continuous, with no SP number repeated in the ID series or vice versa so that there could not be, for example, both an "SP-435" and an "Id. No. 435". The SP and ID numbers were used parenthetically after each boat's or ship's name to identify it; although this system pre-dated the modern hull classification system and its numbers were not referred to at the time as "hull codes" or "hull numbers," it was used in a similar manner to today's system and can be considered its precursor.<ref>Naval History and heritage Command Online Library of Selected Images (archived from [https://web.archive.org/web/20031007233309/http://www.history.navy.mil/photos/shusn-no/spid-no.htm the original] at https://web.archive.org/web/20100329212007/http://www.history.navy.mil/photos/shusn-no/spid-no.htm).</ref>

=== United States Revenue Cutter Service and United States Coast Guard ===
The [[United States Revenue Cutter Service]], which merged with the [[United States Lifesaving Service]] in January 1915 to form the modern [[United States Coast Guard]], began following the Navy's lead in the 1890s, with its [[United States Coast Guard Cutter|cutters]] having parenthetical numbers called [[Naval Registry Identification Number]]s following their names, such as (Cutter No. 1), etc. This persisted until the Navy's modern hull classification system's introduction in 1920, which included Coast Guard ships and craft.

=== United States Coast and Geodetic Survey ===

Like the U.S. Navy, the [[United States Coast and Geodetic Survey]] – a uniformed seagoing service of the [[United States Government]] and a predecessor of the [[National Oceanic and Atmospheric Administration]] (NOAA) – adopted a hull number system for its fleet in the 20th century. Its largest vessels, "Category I" [[Oceanography|oceanographic]] [[survey ship]]s, were classified as "ocean survey ships" and given the designation "OSS". Intermediate-sized "Category II" oceanographic survey ships received the designation "MSS" for "medium survey ship," and smaller "Category III" oceanographic survey ships were given the classification "CSS" for "coastal survey ship." A fourth designation, "ASV" for "auxiliary survey vessel," included even smaller vessels. In each case, a particular ship received a unique designation based on its classification and a unique hull number separated by a space rather than a hyphen; for example, the third Coast and Geodetic Survey ship named ''Pioneer'' was an ocean survey ship officially known as [[USC&GS Pioneer (OSS 31)|USC&GS ''Pioneer'' (OSS 31)]].<ref>[https://books.google.com/books?id=uYSPAAAAMAAJ&dq=Ocean+Survey+Ship+%28OSS%29+MSS+CSS&pg=PA3612 United States Department of State, ''United States Treaties and Other International Obligations, Volume 23, Part Four'', Washington, D.C.:U.S. Government Printing Office, 1972, p. 3612.]</ref><ref>{{Cite web |url=http://docs.lib.noaa.gov/rescue/cgs/011_pdf/CSC-0205.pdf |title=United States Department of Commerce, ''Annual Report of the Director of the Coast and Geodetic Survey for the Fiscal Year Ending June 30, 1964'', U.S. Government Printing Office, Washington, D.C.: 1964, pp. 3–5. |access-date=6 May 2014 |archive-url=https://web.archive.org/web/20130219015620/http://docs.lib.noaa.gov/rescue/cgs/011_pdf/CSC-0205.pdf |archive-date=19 February 2013 |url-status=dead }}</ref> The Coast and Geodetic Survey{{'}}s system persisted after the creation of NOAA in 1970, when NOAA took control of the Survey{{'}}s fleet, but NOAA later changed to its modern hull classification system.

=== United States Fish and Wildlife Service ===

The Fish and Wildlife Service, created in 1940 and reorganized as the [[United States Fish and Wildlife Service]] (USFWS) in 1956, adopted a hull number system for its [[Fisheries science|fisheries]] [[research ship]]s and [[patrol vessel]]s. It consisted of "FWS" followed by a unique identifying number. In 1970, NOAA took control of the seagoing ships of the USFWS's Bureau of Commercial Fisheries, and as part of the NOAA fleet they were assigned new hull numbers beginning with "FRV," for Fisheries Research Vessel, followed by a unique identifying number. They eventually were renumbered under the modern NOAA hull number system.