This entire site, including all its pages, is copyright © Stephen S. Roberts, 2001-2013 or later as indicated.

U. S. Navy Section Patrol (SP)
and Identification (ID) Numbers, 1916-1941

Source Citations

This list was compiled over a period of 40 years from various official U.S. Navy sources. Although much of it is in rough manuscript form, it seemed worth posting as it is probably the only such listing in existence covering the entire period from 1916 to 1941 during which these SP and ID numbers were in use. These numbers were used operationally to identify ships during World War I, and after the Navy adopted its standard hull number system in July 1920 they continued to be used in mobilization war planning for ships not on the Navy List. The various parts of the list came primarily from the following sources:

SP-1 to ID-3679: From a file of 5 x 8-inch S.P. (SP) data cards located in the Ships Histories collection at the Naval History and Heritage Command in Washington, D.C.

ID-3680 to ID-4656: From the above card file and from inspection reports for 1916-1925 located in the U.S. National Archives, Record Group 19 (Bureau of Construction and Repair), Entry 88 (Correspondence, "A" Documents), 1912-1925, subject number 1502-A (conversion of civilian vessels), file (case) numbers up to 6139 (individual vessels). For example file 1502-A-2370 contains the inspection report for S.S. CAROLYN (ID-1608).

ID-4657 to ID-4995: From inspection reports for 1925-1939 located in the U.S. National Archives, Record Group 19, Entry 115 (General Correspondence), 1925-1940, file symbol QS1-(ID number), boxes 3860 to 3872. For example, the file symbol QS1-(4807) contains the inspection report for S.S. HAVANA (ID-4807). A few reports are in Record Group 19, UD-1 (Confidential Correspondence), 1925-1940, same file symbol, boxes 120-121.

ID-4996 to ID-5032: From WPL-10 war planning documents located in Record Group 38 (Chief of Naval Operations), Entry 355 (A-1) (Strategic Plans/War Plans Division, 1912-46), boxes 10 to 13, particularly Changes 10 and 11 in Box 13. The inspection reports for 1940-1941 have not been located.

Notes and Illustrations

Click on the small photograph to prompt a larger view of the same image or to load the corresponding PDF file.

The S.P. data card file contains a card for nearly every vessel between SP-1 and ID-4609 plus the cards reproduced here that list in numerical order all vessels between SP-1 and ID-3679. These cards appear to have been created in the Bureau of Construction and Repair using data and photographs from inspection reports and were then used to record additional information from correspondence on the vessels, including the acquisition and disposal of some of them by the Navy during World War I. These cards were extensively used by the authors of the Dictionary of American Naval Fighting Ships. Shown here is the card for the motor boat ARAWAN II (SP-1).

Photographs were included in many inspection reports, particularly the earlier ones, and copies were attached to the corresponding S.P. data cards. Many of these photographs were posted in the "Online Library of Selected Images" of the Naval History and Heritage Command and, although no longer available there, are still (2015) available in the unofficial mirror of the "Online Library" hosted by HyperWar. Shown here is the photograph of ARAWAN II (SP-1) from her S.P. data card as posted on the Online Library.


A rare case of a large World War I acquired ship displaying a number. Section Patrol craft, initially motor boats and yachts, normally displayed their SP (S.P.) numbers while ocean-going ships never displayed their ID numbers. This ship, S.S. BERKSHIRE, was a 2,000-tons passenger ship but was assigned to the Section Patrol force while serving as a training ship for paravane equipment. BERKSHIRE, built in 1881, was apparently considered too old for regular ocean-going duty. (Source: U.S. National Archives, Record Group 19-E, box 1, folder X.)

By the early 1920s inspection reports contained up to 27 numbered pages plus additional sheets as needed. This PDF file contains selected pages from the 1928 report for S.S. HAVANA (ID-4807), which was the former USS COMFORT (AH-3) totally rebuilt after being sold back into civilian service in 1925.
The 1928 inspection report for S.S. HAVANA (ID-4807) contained this artist's concept of the rebuilt Navy hospital ship. This ship had been S.S. HAVANA before the Navy acquired her in July 1917 but did not receive an ID number. Her sister, S.S. SARATOGA, was taken over in late September 1917 and received one of the earliest ID numbers given to a large ship, ID-1305. SARATOGA served until 1938 as USS MERCY (AH-4).


One-page characteristics cards were also used after about 1920 to document inspections. Shown here is the 1939 characteristics card for S.S. TAKU, ex ORMES (ID-4994). Her sister TYEE, ex ORITONI (no known ID number), became USS MIDWAY (AG-41) in 1942.

The WPL-10 mobilization planning documents produced between 1924 and 1941 contained long lists of "vessels not on the Navy List" with their ID numbers. Shown here is the page in WPL-10 Change 11 of December 1940 that contains the highest number, ID-5032, found in these reports. One last number, ID-5043, was found in the 1940-1945 RG-19 correspondence file for USS SUSAN B. ANTHONY (AP-72), ex S.S. SANTA CLARA.


This entire site, including all its pages, is copyright © Stephen S. Roberts, 2001-2013 or later as indicated.