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

Tanker S.S. J. M. Guffey (ID # 1279)

Tanker S.S. J. M. Guffey (ID # 1279)

Between 1916 and 1941 the U.S. Navy assigned over 5,000 Section Patrol (SP) and Identification (ID) numbers in a single series to ships and craft that it inspected for possible naval use. This page provides links to PDF files that identify the vessels to which these numbers were assigned.
To view or download a PDF file, click on the icon to the right of the description of the file.

The inspection of merchant ships for possible Navy use goes back at least to an Act of Congress approved on 3 Mar 1891 that provided for subsidies to ships providing ocean mail service between the United States and foreign ports. Under this law the Navy was to establish requirements that would ensure that the ships receiving subsidies could be used by the Navy in wartime and was to inspect the ships to ensure that the requirements were met. The inspection program for ocean-going ships expanded greatly as World War I approached, but initially the Navy did not assign the inspected ships identification numbers.

As part of the preparedness campaign of 1916 the Navy began planning for the formation of coast defense "Section Patrols" using privately owned recreational craft. In July 1916 the Navy despatched to the Third Naval District a board to inspect the motor boats that had been enrolled for the September 1916 Motor Boat Cruise, and on 1 Aug 1916 the board directed that these boats be presented for inspection at the Brooklyn Navy Yard before the start of the cruise, preferably in August. Each boat that was found suitable for possible Navy use was assigned a number, prefixed with "S.P." for Section Patrol.


September 1916 - June 1917. These numbers were all assigned to Section Patrol (SP) craft, initially motor boats, soon joined by steam yachts, fishing vessels, tugs, and other small types. The first SP numbers were assigned in September 1916 to motor boats in the New York Motor Boat Cruise that were inspected in August. Ocean-going ships were also being inspected in a separate program but were not being assigned numbers.


June - November 1917. Numbers continued to be assigned exclusively to Section Patrol craft until October 1917 when the Navy stopped taking over vessels for Naval District use and started assigning numbers in the same series to ocean-going ships. The prefix "Id." replaced "S.P." for vessels not assigned to Section Patrols. (These are rendered here and elsewhere as "ID" and "SP.") Many ships between ID-1278 and ID-1601 were ocean-going vessels that had been inspected in 1916 or earlier in 1917 and that received ID numbers in October and November 1917.


November 1917 - March 1918. At first most new numbers continued to be assigned to previously-inspected ocean-going vessels. They were then joined by a disparate mix of newly-inspected ocean-going vessels plus tugs, fishing craft, and other small types. ID-1537 was one of the first of over 500 barges that were inspected, many for use in coaling ships in the Port of New York. Newly-built Shipping Board vessels began to receive numbers towards the end of this period.


March - November 1918. New number assignments contined to cover a mix of types during this period, but the Shipping Board's new construction program (including requisitioned vessels) took an increasingly prominent role. On July 31, 1918 the ID numbers 2987 through 3027 were assigned to ex-German and some other unnumbered vessels already controlled by the Navy for which inspection reports were on file. The number ID-3679 was assigned just as World War I ended.


November 1918 - late 1919. The smaller types of vessels all but disappeared from the inspection program soon after the end of World War I, and thereafter most new numbers were assigned to the Shipping Board's new construction freighters and tankers.


1919 - 1920. During the peak of Shipping Board ship deliveries, the previous practice of using inspections to cover one or more sister ships (which received the ID number of the inspected sister with a letter suffix) was greatly extended. Thus the inspection report for the standard Hog Island freighter LAFCOMO (ID 4253) was also used to represent 60 of her sisters (ID 4253-A through ID 4253-HHH).


1920 - 1925. On October 10. 1921 the ID numbers 4503 through 4548 were assigned to private vessels that had been inspected before the adoption of the current numbering system. On March 7, 1923, around the time ID-4595 was assigned, the Joint Merchant Vessel Board decided that identification numbers would no longer be assigned to vessels until after they had been inspected, largely ending the practice of assigning letter suffixes to ID numbers. As the Shipping Board program tapered off, privately-built cargo ships briefly assumed a prominent role in the inspection list.


1925 - 1941. The merchant vessel inspection program continued throughout the interwar period in support of the Navy's war planning effort. An intensive inspection effort between about 1926 and 1929 included a large number of tankers, needed to support a rapid advance of the fleet across the Pacific. Inspections then slowed down as the Navy's plans became less ambitious. An upsurge in 1936-38 included many yachts and fishing vessels for patrol and mine warfare duty. In 1939, beginning with ID-4992, the practice of assigning suffix letters to sister ships resumed as the Maritime Commission's new construction program began producing many potential naval auxiliary ships.


Please click here for a page with information on sources and samples of some source documents.

Between 1924 and 1941 the Navy maintained a publication, WPL-10, that contained a list of civilian ships suitable for Navy use in case of mobilization with their ID numbers and that also laid out the specifications for the various types of auxiliaries into which they would be converted. The penultimate update of this publication, Change 11, was dated December 1940 and promulgated on 23 January 1941. By this time ID numbers were being incorporated into the title blocks of conversion plans, and the last known number, ID 5043 was assigned around 30 June 1941 to S.S. SANTA CLARA for this purpose. However Change 12 to WPL-10, promulgated on 29 September 1941, retained the conversion specifications but deleted all the lists of ships. This appears to have ended the assignment of ID numbers. WPL-10 itself was cancelled following the U.S. entry into the war in December 1941.

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