Havre Air Force Station Havre Air Force Station ( ADC ID : P - 25 , NORAD ID : Z - 25 ) is a closed United States Air Force General Surveillance Radar station . It is located north - northwest of Havre , Montana . It was closed in 1979 . History . In late 1951 Air Defense Command selected Simpson , Montana as a site for one of twenty - eight radar stations built as part of the second segment of the permanent radar surveillance network . Prompted by the start of the Korean War , on July 11 , 1950 , the Secretary of the Air Force asked the Secretary of Defense for approval to expedite construction of the second segment of the permanent network . Receiving the Defense Secretary ’ s approval on July 21 , the Air Force directed the United States Army Corps of Engineers to proceed with construction . On 1 March 1951 the 778th Aircraft control and Warning Squadron was activated at Simpson and began operating AN / FPS - 3 and AN / FPS - 4 radars . Initially the station functioned as a ground control intercept ( GCI ) and warning station . As a GCI station , the squadron ' s role was to guide interceptor aircraft toward unidentified intruder s picked up on the unit ' s radar scopes . The site was renamed Havre Air Force Station on 1 December 1953 . The Air Force added an AN / GPS - 3 c . late 1958 that stayed until 1965 . During 1961 Havre AFS joined the Semi Automatic Ground Environment ( SAGE ) system , initially feeding data to DC - 20 at Malmstrom AFB , Montana . After joining , the squadron was redesignated as the 778th Radar Squadron ( SAGE ) on 1 March 1961 . The radar squadron provided information 24 / 7 the SAGE Direction Center where it was analyzed to determine range , direction altitude speed and whether or not aircraft were friendly or hostile . On 31 July 1963 , the site was redesignated as NORAD ID Z - 25 . In the early 1960s AN / FPS - 6 and AN / FPS - 6B radars took over height - finder duties . The AN / FPS - 6B was upgraded to an AN / FPS - 90 in 1964 ; it was deactivated in 1969 . In 1965 an AN / FPS - 27 replaced the AN / GPS - 3 as the search radar . In addition to the main facility , Havre operated two AN / FPS - 18 Gap Filler sites : Over the years , the equipment at the station was upgraded or modified to improve the efficiency and accuracy of the information gathered by the radars . The 778th Radar Sq was inactivated and replaced by the 778th Air Defense Group in March 1970 . The upgrade to group status was done because of Havre AFS ' status as a Backup Interceptor Control ( BUIC ) site . BUIC sites were alternate control sites in the event that SAGE Direction Centers became disabled and unable to control interceptor aircraft . The group was inactivated and replaced by the 778th Radar Squadron . as defenses against manned bomber s were reduced . The group was disbanded in 1984 . Havre AFS ceased operations on 1 July 1979 with the inactivation of Aerospace Defense Command . The 778th Radar Squadron was inactivated on 28 September 1979 . The station was re - opened in 1986 as a SAC electronic bomb scoring site . Closed again in the mid / late 1990s . In 199 the station was home to the Anchor Academy , a school for troubled teenage boys , but now that is closed . Today , the former Havre Air Force Station is largely abandoned . A few homes remain in the former military housing area are used as private residences . Air Force units and assignments . Units . Squadron Group