United States Navy 1975 ship reclassification

The United States Navy reclassified many of its surface vessels in 1975, changing terminology and hull classification symbols for cruisers, frigates, and ocean escorts.

From the 1950s to 1975, the Navy had three types of fast task force escorts and one type of convoy escort. The task force escorts were cruisers (hull classification symbols CAG/CLG/CG), frigates or destroyer-leaders (DL/DLG), and destroyers (DD/DDG); the convoy escorts were ocean escorts (DE/DEG), often called destroyer escorts as they retained the designation and number series of the World War II vessels. Added in the early 1970s was a new ocean escort called the patrol frigate (PF), another designation previously used in World War II, which was the initial designation of the Oliver Hazard Perry class. In 1975, these classifications were simplified to cruiser (CG), destroyer (DD/DDG), and frigate (FF/FFG).

Under the pre-1975 classification, cruisers were large vessels, the size of World War II gun cruisers, intended as the primary surface combatants. All but one (USS Long Beach (CGN-9)) were converted World War II gun cruisers (CL/CLG or CA/CAG), carrying either Talos or Terrier surface-to-air missiles (SAMs), and in some cases also Tartar missiles. The primary mission of these ships and the guided missile frigates was to intercept Soviet anti-ship cruise missiles. One cruiser was to be assigned to each carrier group. Most of the cruiser conversions were performed to rapidly deploy the new naval SAMs while the guided missile frigates were being designed and built. There were relatively few cruiser conversions, due to their cost and because the frigates could carry almost as many weapons as a cruiser.

...
Wikipedia