The United States Navy's Boston class were the first guided missile cruisers in the world. Both ships in this experimental class were originally Baltimore-class heavy cruisers that had been decommissioned after World War II, but were redesignated as guided missile heavy cruisers (CAGs) and entered refit in 1952. The lengthy conversion and modernization project involved removing the aft triple 8-inch gun turret and its supporting structure and installation of two twin launchers for Terrier anti-aircraft guided missiles. The forward two 8-inch gun turrets remained unchanged. The forward superstructure was modified to include the Terrier's associated radars and electronics, the aft superstructure was completely replaced, and Baltimore class's two funnels were trunked to one.
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. Had the ships been fully converted, the forward 8-inch turrets would have been replaced with additional Terrier launchers.
In 1968 both Boston class guided missile heavy cruisers were reclassified back to heavy cruisers (CAs), in part due to the extensive use of their 8-inch guns for shore bombardment during the Vietnam War. 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 were once again their six remaining 8-inch guns in the forward turrets.