Site 5of the 556th Strategic Missile Squadron, Plattsburgh. One of 12 Atlas F ICBM sites in NY and VT which ringed Plattsburgh Air Force Base during the Cold War. The silos were 174 feet deep and 54 feet in diameter.
See:
http://www.atlasmissilesilo.com/556thSMS.htm
http://www.siloboy.com/