The James Madison class of submarine was an evolutionary development from the Lafayette class of fleet ballistic missile submarine. They were identical to the Lafayettes except for being initially designed to carry the Polaris A-3 missile instead of the earlier A-2. This class, together with the George Washington, Ethan Allen, Lafayette, and Benjamin Franklin classes, composed the "41 for Freedom" that was the Navy's primary contribution to the nuclear deterrent force through the late 1980s. This class and the Benjamin Franklin class are combined with the Lafayettes in some references.
USS John C. Calhoun (SSBN-630) entering Holy Loch, Scotland on completion of the thousandth Polaris nuclear deterrent patrol, 18 May 1972.