The current squadron traces its lineage back to 15 September 1949, when 2 Air Defence Control Centre (ADCC) was initially established at RCAF Station Chatham, New Brunswick. They were formed to support the fighter interception and training functions for No. 421 (Fighter) Squadron flying the deHavilland Vampire Mk. III. At that time, the unit consisted of little more than eight trucks carrying a World War II vintage radar, known as the AMES II. Total personnel strength, officers and men, was 50.
Construction began in 1950 on RCAF Station St. Margarets, located 12 miles southeast of Chatham. On 1 December 1952, 2 ADCC was disbanded and No. 2 Aircraft Control & Warning Unit took its place to provide control facilities for the fighter squadrons of Air Defence Command; to collect, evaluate, and display information on the air situation within its area of responsibility for use by military agencies and civil defence authorities; to provide (Air Defence) early warning services within the squadron's area of surveillance; and, to commit such air defence forces as may be assigned to it when authorized to do so.
At the beginning of the Korean War, the signing of the Pinetree Agreement meant that St. Margarets would become one of the initial radar sites, known as Group IV sites. The GCI unit moved to its new home at St. Margarets (site C-5), and was activated as a Pinetree Line site on 1 November 1953. At the time they became operational, the unit was reporting to the Fredericton Sector.
While St. Margarets (callsign Midwife) was under construction, operations continued at Chatham. The first radars to equip St. Margarets were the FPS-3 and the dual ISG-98 Height Finders. These radars were later replaced by the AN/TPS-501 Height Finder. In 1957, three new radars were added. These included the FPS-6B Height Finder and the FPS-502 small surveillance radars which brought the total number of radar towers at St. Margarets to six. The FPS-502, though in place, was not needed and was never actually activated. On 8 May 1958, 21 AC&W Squadron was renamed as 21 Radar Squadron, St. Margarets, New Brunswick.
The summer of 1960 saw yet another radar under construction. This time the tower would contain the FPS-507 Height Finder radar. At about the same time a new search radar, the FPS-20 (later re-designated as the AN/FPS-508), replaced the existing radars in place.
In September 1962, St. Margarets became 21 AC&W Squadron and operated under control of the Bangor Sector which was headquartered at Topsham AFB, Maine. St. Margarets became a Long Range Radar upon being SAGE-capable in 1962. Equipment used by the SAGE System included the FPS-508 and two FPS-6B Height Finder radars with information processed by the FST-2 Data Processor. Also a major component of the SAGE was the Ground Air Transmit Receiver (GATR) site and associated antennae arrays. At the same time, they were becoming part of the Back-Up Intercept Control (BUIC) I program so that they could, in effect, take over control of the Bangor Sector should the need arise. The remained part of BUIC I to Bangor until 1966. In early 1966, after Charleston Air Force Station Virginia became a BUIC III computerized facility, St. Margarets, while retaining its primary long range radar role, was designated as a manual back-up intercept control site for BUIC II. BUIC II was to be an interim system lasting until the end of 1968.
While many other radar stations were being re-designated as Canadian Forces Stations, St. Margarets became CFB Chatham, St. Margarets Detachment. Under the third phase of BUIC, St. Margarets was assigned as a BNCC (BUIC NORAD Control Centre) role, becoming operational 1 January 1969 with the callsign "Billy Boy". At this time 21 Radar was designated as BNCC No. 2 with 34 Radar Squadron at Senneterre as BNCC No. 1.
By the spring of 1972, the BUIC system began to wind down. As a result of austerity measures, the United States dictated a partial abandonment of the BUIC System. CFS Senneterre BNCC was put on stand-by status, making St. Margarets the only operational BNCC in the 22nd NORAD Region. 21 Radar was also designated as the Region ALCOP (Alternate Command Post) should anything happen to North Bay.
In 1974, St. Margarets was selected as a Satellite Tracking and Identification (SITU) location and by 1976, the SITU was operational. They continued with this task until closure in 1989.
During the period 1 October 1980 to 14 June 1983, from the hours of 1530 to 2330 local time, St. Margarets was the controlling agency for the 22nd NORAD Region. While the new ROCC (Regional Operational Control Centre) facilities were being introduced at the underground facility in North Bay late in 1983. St. Margarets provided operational back-up during the testing trials and acceptance period. The ROCC's were fully operational by August 1984 with St. Margarets incorporated into Canada East. On 19 July 1983, 21 Radar Squadron relinquished their BUIC and ALCOP taskings and reverted to a Long Range Radar (LRR) Site.
By now, the writing was on the wall as to St. Margarets future as other radar sites were closing at an alarming rate. In March 1985, fears were confirmed when the Minister of National Defence announced the impending closure of the CADIN/Pinetree Line, and among its victims, St. Margarets. The final day came on 1 April 1988, ironically the 64th anniversary of the Royal Canadian Air Force.
Today the legacy of 21 Squadron can be found at 22 Wing North Bay Ontario where a vital air defence mission is still being performed. The squadron was resurrected as 21 Aerospace Control and Warning Squadron in the fall of 1988. One of the two ROCC's, Canada East, was re-designated 21 AC&W Squadron; quite befitting for the unit whose motto is "Intruder Beware". On 6 October 1988, 21 AC&W Squadron reformed in North Bay as the operational squadron responsible for Canada East ROCC. Today, 21 Squadron is the operational squadron within North Bay and operates both Canada East and Canada West sectors within the same amalgamated Operations Room located on the ground floor of the Underground Complex.
--The NBC Group - Don Nicks, John Bradley, Chris Charland.