USS Tracer (AGR-15)


USS Tracer (AGR-15) was a Guardian-class radar picket ship, converted from a Liberty Ship, acquired by the US Navy in 1957. She was reconfigured as a radar picket ship and assigned to radar picket duty in the North Pacific Ocean as part of the Distant Early Warning Line.

USS Tracer (AGR-15).jpg
USS Tracer (AGR-15) underway, date and location unknown.
United States
NameWilliam J. Riddle
NamesakeWilliam J. Riddle
OwnerWar Shipping Administration (WSA)
OperatorMoore McCormack Lines, Inc.
Orderedas type (EC2-S-C5) hull, MC hull 2340
BuilderJ.A. Jones Construction, Panama City, Florida[2]
Yard number81
Way number5
Laid down24 December 1944
Launched31 January 1945
Sponsored byMrs. Marion Harders
Completed15 February 1945
United States
  • Interrupter (1958)
  • Tracer (1959–1965)
  • One who breaks in upon some action, hinders, or obstructs
  • One that traces, tracks down, or searches out
Commissioned16 October 1958
Decommissioned7 July 1965
Renamed4 September 1959
ReclassifiedGuardian-class radar picket ship
RefitCharleston Naval Shipyard, Charleston, South Carolina
Stricken1 September 1965
United States
General characteristics [4]
Class and type
  • 441 feet 6 inches (135 m) oa
  • 416 feet (127 m) pp
  • 427 feet (130 m) lwl
Beam57 feet (17 m)
Draft27 ft 9.25 in (8.4646 m)
Installed power
  • 2 × Oil fired 450 °F (232 °C) boilers, operating at 220 psi (1,500 kPa)
  • 2,500 hp (1,900 kW)
Speed11.5 knots (21.3 km/h; 13.2 mph)
Capacity490,000 cubic feet (13,875 m3) (bale)
General characteristics (US Navy refit)[3]
Class and typeGuardian-class radar picket ship
  • 443,646 US gallons (1,679,383 l; 369,413 imp gal) (fuel oil)
  • 68,267 US gallons (258,419 l; 56,844 imp gal) (diesel)
  • 15,082 US gallons (57,092 l; 12,558 imp gal) (fresh water)
  • 1,326,657 US gallons (5,021,943 l; 1,104,673 imp gal) (fresh water ballast)
  • 13 officers
  • 138 enlisted
Armament2 × 3 inches (76 mm)/50 caliber guns

Because of the closeness of the sound of names issued for radar picket ships at the time, Interrupter had her name changed by the Navy to Tracer so as not to confuse her with USS Interdictor (AGR-13) and USS Interpreter (AGR-14)


Tracer (AGR-15) was laid down on 24 December 1944, under a Maritime Commission (MARCOM) contract, MC hull 2340, as the Liberty Ship Dudley H. Thomas, by J.A. Jones Construction, Panama City, Florida. She was launched 31 January 1945; sponsored by Mrs. Marion Harders; and delivered 21 February 1945, to the Moore McCormack Lines, Inc.[3][5]

Service historyEdit

Merchant serviceEdit

William J. Riddle operated with Moore-McCormack Lines and the Waterman Steamship Corporation from 1945 to 1947. When hostilities ended in the Far East in mid-August 1945, she was steaming from Hawaii to the Philippines.[5]

Converted to a cattle carrier the following year, she operated as such through the end of 1946. Changed back to a dry cargo carrier by March 1947, she voyaged to European and Mediterranean ports until the summer of 1947, when she was laid up in MARCOM's James River Reserve Fleet, Lee Hall, Virginia. She remained there for 10 years.[5]

US Navy serviceEdit

The Navy selected William J. Riddle for conversion to a radar picket ship in May 1957. Towed to the Charleston Naval Shipyard, Charleston, South Carolina, conversion work began on 24 May 1957. Renamed Interrupter, and classified as AGR-15, she was commissioned at Charleston, 16 October 1958.[3][5]

Following shakedown in Guantanamo Bay, Cuba, and post-shakedown availability at her conversion yard, Interrupter sailed for the Pacific Ocean. She transited the Panama Canal, on 26 January 1959, and arrived at her home port, San Francisco, California, on 12 February, the sixth AGR to join newly formed Radar Picket Squadron 1.[5]

Fitted out with the latest radar detection equipment, Interrupter and her seven Guardian-class radar picket ship sister ships were designed to serve as the seaborne eyes of the North American Air Defense Command (CONAD), the naval link in the chain of early-warning stations covering the Pacific approaches to the United States. Her mission was to "detect, report, and track enemy airborne threats approaching by overseas routes and to control the intercepts used to destroy such threats."[5]

Before putting to sea for her first patrol, she conducted training evolutions with U.S. Air Force officers embarked on board for familiarization with the ship's mission. In addition, Interrupter's, officers and men familiarized themselves with the Air Force's part in this vital mission. On 6 March 1959, Interrupter sailed from San Francisco on her first barrier patrol.[5]

On 4 September 1959, Interrupter was renamed Tracer to eliminate confusion with some of her sister ships with similarly sounding names.[5]

Between 1959 and 1965, Tracer conducted patrols at sea, at various picket stations in the Western Contiguous Radar Line. The ship proved to be an efficient vessel and received awards for administrative and operational efficiency on several occasions. As more sophisticated early-warning systems came into operational use, the need for the AGR's diminished accordingly.[5]


Deactivated in 1965, Tracer's name was struck from the Navy List on 1 September 1965. She was then transferred to the US Maritime Commission (MARCOM) and laid up at the Suisun Bay Reserve Fleet, Suisun Bay, California, where she remained until sold, 15 July 1974. Before being scrapped in China in 2000, Tracer, renamed Unisea, served as a fish processing plant in Unalaska, Alaska.[3][5]

Honors and awardsEdit

Tracer's crew was eligible for the following medals:




  • "Tracer". Dictionary of American Naval Fighting Ships. Navy Department, Naval History and Heritage Command. 30 September 2015. Retrieved 5 December 2019.  This article incorporates text from this source, which is in the public domain.
  • "Jones Construction, Panama City FL". 13 October 2010. Retrieved 5 December 2019.
  • Davies, James (May 2004). "Specifications (As-Built)" (PDF). p. 23. Retrieved 5 December 2019.
  • "SS William J. Riddle". Retrieved 5 December 2019.
  • "USS Tracer (AGR-15)". 8 February 2019. Retrieved 5 December 2019.

External linksEdit

  • Photo gallery of USS Tracer at NavSource Naval History