The original 110-foot subchasers of World War I were built before hull numbers came into universal Navy use. They were given "number" names; Submarine Chaser No.1, No.2, and so on. This was abbreviated in the Navy Register as S.C. 1, etc.; this designation, without punctuation, was also painted on the ships' bows.

On 17 July 1920, the Navy adopted its system of letter-number hull numbers. Patrol vessels received letter type symbols beginning with P, and submarine chasers were designated PC. They retained their letter-number names, abbreviated "S.C.," but now also had hull numbers beginning with "PC-." Thus, for instance, USS S.C. 64 (PC-64). Relatively few 110- footers remained by this time, many having been disposed of after the war's end, but they were given the same PC- series numbers that they had borne as names. During the years between the wars, the punctuation was gradually dropped from the
"S.C." names.

World War II expansion programs led to construction of two large groups of subchasers, the new 110-foot wooden-hulled craft and the 173-foot steel-hulled type. By 1943, it was felt desirable to differentiate between the two types. The type symbol PC was retained for the steel 173-footers, and the separate symbol SC was adopted for the 110-foot vessels. These now dropped the dual "S.C.-PC" identification, and were simply identified as "USS SC-." As noted earlier, some SCs and PCs were later modified for amphibious control work and redesignated SC(C) and PC(C), retaining the same numbers. Several types of patrol craft, including PC, SC, PCE, PCE(R) and PCS were given numbers from the same general numerical series, explaining the gaps in the number sequence for SCs and PCs.

Early PC's were converted yachts acquired by the Navy. These together with the 362 World War II built PCs replaced the larger and more valuable DD's and DE's around harbors and restricted waters. The 173 foot World War II constructed PC was steel hulled, twin diesel propelled and armed with a dual-purpose 3"/50 and 40mm gun. Later the 3"/50 was replaced with a single Bofors 40mm and three single 20mm guns were added. PCs carried a considerable amount of detection and ranging gear for locating submarines. They were capable of a speed of about 18 knots and were highly maneuverable. The Steel-hulled PC-461 Class ships were built in three series; PC-461 to PC-496 (36), PC-542 to PC-627 (86), PC-776 to PC-826 (51), PC-1077 to PC-1265 (189). Some PCs were converted to Amphibious Control Vessels and reclassified PCC.

In addition to 403 173-foot PC-class patrol craft ordered for the U.S. Navy in 1941, eighteen 173-foot hulls were ordered for use as minesweepers, as the Adroit class. Built by five yards, all but three of the minecraft variant had been commissioned by the end of 1942, and the last entered service the following June. Unlike the PCs, AM 82-99 were given names: Adroit, Advent, Annoy, Conflict, Constant, Daring, Dash, Despite, Direct, Dynamic, Effective, Engage, Excel, Exploit, Fidelity, Fierce, Firm, and Force, respectively. As completed, they differed from the PCs in having a large sweep-cable reel mounted on the first platform deck and protruding through the main deck at the stem, in place of the after 3-inch or 40-mm gun mount; a slightly longer superstructure, surrounding the squat dummy funnel at its after end; a kingpost and boom fitted to handle minesweeping gear and the 16-foot-wherry; and two davits at the stem to handle sweep gear and reload depth charges.

AM 82 through 88, built at Portland, Oregon, saw service throughout World War II in the Pacific. Only the Annoy (AM-84) is recorded as having been used to sweep for mines, in Aleutian waters; the others principally were employed as convoy escorts in the dangerous waters of the southwest Pacific. The other 11 operated initially either from Bermuda (AM-89 to 93) or from mainland U.S. bases, again as convoy escorts. That they were far more useful in an antisubmarine role than as minecraft was realized quickly, and the 11 Atlantic units were cycled through the Norfolk Navy Yard during May and June 1944 to have their mine countermeasures gear removed and additional antisubmarine and antiaircraft ordnance added. The Pacific units were modified at Pearl Harbor. On 1 June 1944, all 18 lost their names and were reclassified PC-1586 through 1603.

Of the 11 Atlantic units, PC-1593-1597 were sent to the Mediterranean, where they saw service during the landings in France in August 1944 and elsewhere as local escorts. They returned to Jacksonville, Florida, in June 1945, seeing no further action. PC-1598-1603 were dispatched to the Pacific in July 1944 and escorted support convoys as U.S. forces drew closer to the Japanese homeland. During the invasions at Okinawa and lwo Jima, several were used as inshore control ships for landing craft, and two were further reclassified as control craft PCC-1599 and PCC-1601 in the summer of 1945. Only PC-1601 (ex-Fierce, AM-97) was lost during the war, on 21 May 1945. With the exception of the mothballed PC-1590 (ex-Constant, AM-86), which was recommissioned in May 1950 as a Naval Reserve training craft and served in that capacity until October 1954, the survivors were decommissioned quickly postwar and disposed of.

There were 68 Patrol Craft Escort vessels built and delivered to the US Navy and an additional 17 delivered under the Lend-Lease Program to Allies during World War II PCEs were an inexpensive substitute for larger and more valuable DD's and DE's. Though not much longer than the PC the 180 foot steel hulled PCE's tonnage is more than twice as great. Its speed is 15 knots, diesel propelled and armed with a dual-purpose 3"/50 gun, three 40mm guns, five 20mm guns, two depth charge tracks, and ten K-Guns. PCEs carried a considerable amount of detection and ranging gear for locating submarines. The PCE was designed for general escort work, whereas the PC normally stayed near harbors and worked only with coastal convoys. Some PCEs were converted to PCE(R), Rescue Escorts while others were converted to Amphibious Control Vessels, PCE(C).

There were 59 PCS' delivered to the U.S. Navy during World War II. The others were reclassified as Auxiliary Motor Minesweepers (YMS), Survey ships (AGS) or Coastal Minesweepers (AMc).