4 × General Electric geared steam turbines The United States Navy's Boston class were the first guided missile cruisers in the world.

The lengthy conversion and modernization project (aka SCB 48) involved replacing the aft triple 8-inch gun turret and its supporting structure with two twin launchers for Terrier anti-aircraft guided missiles.

[1] Owing to the Boston class's experimental nature, the ships were only partially converted, with a full conversion to be carried out if the new weapon systems were successful.

While they had retained their Terrier missiles, the swift advance of technology had made these pioneering weapons obsolete after little more than a dozen years' service, and the ships' main battery was once again their six remaining 8-inch guns in the forward turrets.

In 1970 both Boston class ships were decommissioned for the final time, eventually struck from the Naval Vessel Register, and sold for scrap.