During the period 1961 and 1963, 12 "Atlas F" missile sites were constructed within a 50-mile radius of the base, thus giving the 380th the capability to launch 12 missiles. All sites were in New York state, except for two located on the other side of Lake Champlain in Vermont. The 556th Strategic Missile Squadron, formerly assigned to Dow AFB, Maine, was transferred to Plattsburgh AFB on 1 October 1961, and became completely operational on 20 December 1962. It was inactivated on 25 June 1965.