thumb|The 25-ton North blast door in the Cheyenne Mountain nuclear bunker is the main entrance to another blast door in the background, beyond which the side tunnel branches into access tunnels to the main chambers. Canada's NORAD bunker at CFB North Bay with a SAGE AN/FSQ-7 Combat Direction Central computer was constructed from 1959 to 1963. Each of the USAF's eight smaller AN/FSQ-8 Combat Control Central systems provided NORAD with data and could command the entire United States air defense. The RCAF's 1950 "ground observer system, the Long Range Air Raid Warning System", was discontinued.Canadian Long Range Early Warning (letter to HQ WADF), CONAC, 16 October 1950 (cited by Schaffel p. 138 & 304) In January 1959, the United States Ground Observer Corps was deactivated.
thumb|The 25-ton North blast door in the Cheyenne Mountain nuclear bunker is the main entrance to another blast door in the background beyond which the side tunnel branches into access tunnels to the main chambers. Canada's NORAD bunker at CFB North Bay with a SAGE AN/FSQ-7 Combat Direction Central computer was constructed from 1959 to 1963. Each of the USAF's eight smaller AN/FSQ-8 Combat Control Central systems provided NORAD with data and could command the entire United States air defense. The RCAF's 1950 "ground observer system, the Long Range Air Raid Warning System", was discontinued.Canadian Long Range Early Warning (letter to HQ WADF), CONAC, 16 October 1950 (cited by Schaffel p. 138 & 304) In January 1959, the United States Ground Observer Corps w,as deactivated.