(Click photo for larger image) (Pan Am Photo)
Perimeter Acquisition Radar (Safeguard PAR)
The 120 foot high PAR building sits on a plain just east of the Pembina Escarpment near the hamlet of Concrete, N.D. For a time, it was the second tallest building in North Dakota. The sloping face of its immense phased array antenna pointed north to detect nuclear warheads fired by the Soviet Union or China as they passed over the north pole.
Built with 17 million pounds of steel reinforcing rods and 58,000 cubic yards of concrete, the PAR was hardened against nuclear blast effects and shielded from the effects of elctro-magnetic pulse (EMP) produced by nuclear detonations. An underground power plant located immediately west of the PAR allowed it to operate autonomously while "buttoned up" during nuclear attack. The PAR site also contained administration and housing areas.
Following deactivation of the Safeguard system in 1976, the PAR was transferred to the U.S. Air Force, which currently operates the radar as part of its space track and early warning system. General Electric was primary contractor for the PAR radar system.
For more information about the PAR, see ABM R & D at Bell Laboratories: Project History
Part II, Chapter 8