The contract to build her was awarded to the Electric Boat Division of General Dynamics Corporation in Groton, Connecticut on 9 June 1960 and her keel was laid down on 14 April 1961. Originally laid down as the eleventh submarine in the Thresher-class building program, Flasher was extensively modified during the construction period. These modifications consisted of lengthening the hull, lengthening the sail, and upgrading the watertight integrity of the sea water systems. The SUBSAFE Program was developed as a result of the loss of the Thresher (SSN-593), the first submarine of the class; Flasher became the first submarine certified as SUBSAFE. This contributed to the lengthy delay between being laid down and commissioning.