The Benjamin Franklin-class submarine was a group of US ballistic missile submarines that were in Navy service from the 1960s–2000s. The class was an evolutionary development from the earlier James Madison class of fleet ballistic missile submarine. Having quieter machinery and other improvements, it is considered a separate class. A subset of this class is the re-engineered 640 class starting with USS George C. Marshall (SSBN-654). The Benjamin Franklin class, together with the George Washington, Ethan Allen, Lafayette, and James Madison 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 James Madison class are combined with the Lafayettes in some references.