Mid - Canada Line The Mid - Canada Line , also known as the McGill Fence , was a line of radar stations across the " middle " of Canada to provide early warning of a Soviet bomber attack on North America . It was built to supplement the less - advanced Pinetree Line , which was located further south . The majority of Mid - Canada Line stations were used only briefly from the late 1950s to the mid - 1960s , as the attack threat changed from bombers to ICBM s ; the early warning role passed almost entirely to the more capable DEW Line further north . History . Impetus . Construction of the Pinetree Line had only just started when air planners started to have concerns about its capabilities and siting . By the time it detected a potential attack by jet - powered aircraft , there would be little time to do anything before the attack reached Canadian or northern U . S . cities . Additionally the Pinetree systems used " old " pulse - based radars that were fairly easy to jam and were unable to detect targets close to the ground due to scattering . Although expensive in terms of fuel use , it would be possible for Soviet bombers to evade detection by flying lower . They would eventually be seen as they approached the stations , but possibly so late that there would be no possibility of intercepting them . This made the Pinetree Line ' s usefulness somewhat suspect even before it had become operational . Dr . W . B . Lewis , head of the AECL Chalk River Laboratories and former Chief Superintendent of the UK Telecommunications Research Establishment ( TRE ) had proposed to the Defence Research Board ( DRB ) a Doppler radar system that avoided both of these problems . Known today as a " forward scatter bistatic radar " , it used two antennas , a transmitter and receiver , separated by about 60 km . Any aircraft flying between the antennas would be detected when it entered the beam , causing the received signal to change . Since the system relied on the speed of the aircraft to " shift " the frequency due to the Doppler effect , the radar could be aimed at static objects like the ground ; although a signal would be reflected and received , since the ground is not moving this signal has no frequency shift and can be easily filtered out . Another advantage of the system is that it requires much less power to operate effectively . A conventional pulse radar spends most of its time turned off , listening for the reflections of its own signal . To ensure the reflections have enough energy to be detected , each pulse has to be extremely powerful . In a bistatic radar the signal is continually broadcasting and even tiny changes in the frequency can be seen and amplified , so a much smaller signal is needed . Compared to the existing Pinetree radars , Lewis ' system would require much smaller sites and less power . The major disadvantage of the system is that it did not indicate the aircraft ' s location within the beam , simply an indication of which beam had been " broken " . Lewis proposed a system in which two overlapping lines of stations would be set up , forming a continuous " fence " . This not only allowed one of the lines to cover the dead points directly over the antennas of the other , but also allowed the location of the aircraft to be determined within 30 km depending on which pair of beams were broken – a distance well within the detection ranges of interceptor aircraft radar . Lewis ' design would be able to see any aircraft from ground level up to 65 , 000 ft . Spider Web . The DRB decided to pursue Lewis ’ idea in 1950 - 51 by directing a research contract to the Eaton Electronics Research Laboratories of McGill University , headed by Professor Garfield Woonton . Lewis suggested to DRB and Woonton that he put the project in the hands of Associate professor , Dr . J . Rennie Whitehead as project leader , working for the University on behalf of the Defence Research Board . Some preliminary tests were made in 1952 with ' breadboard ' hardware , built by a graduate student , Hugh Hamilton , in order to confirm the validity of the idea . In the meantime RCA Victor had been brought in by the DRB to design and produce the receivers , transmitters and antennae for tests on a substantial scale . The testing was performed in the summer of 1953 , when Whitehead and his team of RCA Victor and RCAF personnel installed and operated a string of seven stations stretching from Ottawa to Mattawa along the Ottawa River valley . Known under the code name of " " Spider Web " " , the tests were made with aircraft from Air Defence St . Hubert , near Montreal . All observations were transmitted to and made in the line HQ , which was set up in the equipment hut of one of the seven stations in Deep River . Andrew Matthews of the 104 Communications Flight at RCAF St . Hubert arranged for a series of different aircraft to fly through the network , including an Auster light aircraft , a T - 33 Shooting Star , an Avro Lancaster bomber and even a recently acquired de Havilland Comet jet transport . The tests revealed a great deal about the spectral ‘ signatures ’ of aircraft crossing the line at different points , and demonstrated the capability to detect all sizes of aircraft from 100 ft to over 40 , 000 ft in altitude . During this time Dr . Ross Warren of RCA Victor and Dr . Whitehead jointly developed the theoretical background for the work in a major report to DRB . The Spider Web trials were followed in 1954 by intensive tests on a single link , built in the Eastern Townships for Bell who had by this time been given the go - ahead for the implementation of the Mid - Canada Line . The trials on this prototype link were also conducted by Whitehead and a small team in collaboration with Air Defence Command , St . Hubert , this time on behalf of Bell . The trials involved the flyover of numbers of B - 52 bombers by arrangement with Strategic Air Command and a local bombplot unit . They also had full - time use of an Avro Lancaster from CFB Greenwood for the important low - level tests . The senior uniformed member of the team , Flight Lieutenant Andy Matthews , arranged and navigated all the Spider Web and Eastern Township flight tests . Deployment studies . In February 1953 the Canada - U . S . Military Study Group ( MSG ) was asked " to study those aspects of the North American Air Defence System in general , and the early warning system in particular , which are of mutual concern to the two countries . " The MSG then asked the air defence commanders of Canada and the United States to prepare independent briefs on the subject . By July 1953 , RCAF Air Defense Command had completed its brief , followed shortly thereafter by its USAF counterpart . Both reports suggested building a Doppler fence farther north , along the 55th parallel north , roughly at the entrance of James Bay into Hudson Bay . In October 1953 the MSG recommended to both governments " that there be established at the earliest practicable date , an early warning line located generally along the 55th parallel between Alaska and Newfoundland " , and outlined their minimum operational requirements . By the end of November 1953 , the Mid - Canada Line had been approved in principle . Unlike the jointly - operated Pinetree line and future DEW line , the Mid - Canada line would be funded and operated entirely by the RCAF . The DRB estimated that the system would cost about $ 69 , 700 , 000 , while an independent RCAF report placed it at $ 85 , 000 , 000 . In December an effort started to try to understand what sort of problems would be encountered during construction . Several " trains " consisting of tractor - pulled sleighs set out cross - country . One , manned by the RCAF , set out eastward from Fort Nelson , BC in order to link up with a second moving west from Flin Flon , Manitoba , while a third crewed by the Army left Lake Nipigon near Thunder Bay , Ontario for Lansdown House about 200 km further north . The missions proved that it was possible to build the new line , but only during the winter when the muskeg was frozen solid . These missions also inspired the U . S . Army to invest in purpose - built overland train s which they experimented with in the 1960s but never put into production . While that was taking place , efforts were underway to start primary siting studies . It quickly became clear that the areas in question , at least in eastern Canada , were so remote that there was no really accurate topographical information . A huge effort to map the area in a 15 - mile wide strip across the entire country was started by Transport Command almost immediately , and ended by the spring of 1954 . With this information in hand a construction division was set up , the Systems Engineering Group ( SEG ) , in February 1954 , tasked with producing a final report on the system to be submitted on June 1 . Finalizing the plans . As the experiments continued it became clear that the radar stations could be located further apart , up to 90 km , reducing the number of stations required . Nevertheless the price rose , now estimated at about $ 120 , 000 , 000 . Although their final report was not yet ready , the SEG put in an interim report in June and it was approved by cabinet by the end of the month . In their report they outlined the system that would be built almost exactly . It called for eight major " Sector Control Centres " , numbered from 200 to 900 , each of which control up to thirty unmanned radar sites for a total of 90 radar stations . Each of the radar stations consisted of a single tall mast with a number of small dishes in fixed positions on top ( typically four , two pointed in either direction ) , with power and electronics located in a building below the mast . The sector control centres were linked using an advanced microwave communications system developed in part by CARDE , which scattered off the troposphere for long - distance communications . The southernmost site along the eastern portion of the line , at Cape Henrietta Maria on Hudson Bay , was used as the main communications point , and three additional repeater stations transferred data from the line southward to the NORAD command center in North Bay , Ontario . The easternmost station at Hopedale , Labrador was co - located with an existing Pinetree Line station in order to save construction costs . All aircraft transiting the line would have to file a flight plan through the Mid Identification Zone , or MIDIZ , centred on the fence . The plans also called for the construction of several airbases known as " Line Clearance Aerodromes " just to the north of the line , where interceptor aircraft could operate in times of heightened alert . At about this time another huge civil engineering project was underway in Canada , the construction of a cross - Canada microwave relay telephone system . Since many of the logistics problems were similar , the construction group , led by Bell Canada , was selected as a major contractor for the base construction . Detailed site selection started in 1955 , with a major surveying effort running across Canada at the 55th parallel . The sites were so remote that the RCAF had to form up its first all - helicopter squadron in order to provide flight support for the survey teams . Construction and service . Construction started in 1956 and proceeded quickly . By April 1957 the eastern half was operational , and the line was declared fully operational on January 1 , 1958 . Operations were shortly integrated into the newly - formed NORAD . Even the SEG ' s revised estimates turned out to be too low , and the fence ' s final cost is estimated at $ 224 , 566 , 830 . It was not long before the RCAF started to have reservations about the costs of maintaining the Line . Although technically more capable than Pinetree , the MCL gave little information in terms of planning a response or vectoring interceptors to their targets , these tasks still required the Pinetree radars much further south . The extra time offered by the MCL was not considered worth the trouble of keeping the line operational . Even before the line became operational , in a repeat of earlier history , a new and more capable line was already under study that would combine the plotting capability of the Pinetree system with the line - breaking capabilities of the MCL , and located much further north to dramatically improve the detection and response times . Emerging as the Distant Early Warning Line , or DEW , construction started before the MCL had become operational . When the DEW line became operational in 1957 the value of the MCL was eroded , and the RCAF started pressing for it to be dismantled . The USAF disagreed , but the western half of the line was shut down in January 1964 , leaving the eastern half to help defend the industrial areas of Canada and the US . However as the Soviet Union moved their offensive capability to ICBMs it became clear that both the MCL and Pinetree systems were of limited use , and the entire Mid - Canada line was shut down in April 1965 . The operations site located at Cranberry Portage , Manitoba , for example , has been converted into a high school and residence since active operations at the site closed in the mid - 1960s . Mid - Canada Line POL Supply Points . Petroleums , Oils and Lubricants ( POL ) Supply Points were distribution centers for consumable petroleum materials used to fuel and maintain the Mid - Canada Line DDS sites . Co - located with Sector Control Stations when possible , petroleum products were received in bulk and shipped out by air from these locations .