Which submarine became the first ballistic-missile submarine to conduct a deterrent patrol?

USS George Washington became the first ballistic-missile submarine to conduct a deterrent patrol.

The U.S. Navy’s USS George Washington began the first Polaris deterrent patrol on 15 November 1960. It carried sixteen UGM-27 Polaris missiles, giving the United States a mobile nuclear force that could remain hidden beneath the ocean. The patrol lasted 67 days and ended at the naval base at Rota, Spain.

This achievement helped establish the submarine leg of the U.S. nuclear triad. Unlike land-based missiles, a submerged ballistic-missile submarine was difficult for an opponent to locate and destroy before it could respond.

George Washington is sometimes confused with USS George Washington Carver or later Ohio-class boats. Those ships were also ballistic-missile submarines, but they entered service after the 1959-launched lead boat of the George Washington class had pioneered continuous patrols.