After the war, only six Baltimores (St. Paul, Macon, Toledo, Columbus, Bremerton, and Helena) and two Oregon City-class ships (Albany and Rochester) remained in service, while the rest were moved to the reserve fleet.

However, all ships except Boston, Canberra, Chicago, and Fall River were reactivated for the Korean War.

Except for St. Paul, all the ships retaining all-gun configurations had very short (18 years or less) service lives, and by 1971 were decommissioned, and started being sold for scrap.

With the start of the war, the limitations instituted by the Second London Naval Treaty, which had completely banned the construction of heavy cruisers, became obsolete.

The Baltimore class was based partly on USS Wichita, a heavy cruiser from 1937, which represented the transition from inter-war to World War II designs.

In profile, the Baltimores looked very much like the Cleveland-class light cruisers, the obvious difference being that the larger Baltimores carried nine 8-inch (203 mm) guns in three triple turrets, compared to the twelve 6-inch (152 mm) guns in four triple turrets of the Clevelands.

With the construction of the first eight Baltimore-class ships moving slowly, the US Navy used the time to review the initial plans and improve them.

By 1947, nine of the Baltimores had been decommissioned and placed in the reserve fleet, while seven (Helena, Toledo, Macon, Columbus, Saint Paul, Rochester, and Albany) remained in service.

However, at the start of the 1950s, six were reactivated (Macon had been decommissioned for four short months: June–October 1950), making thirteen available for deployment in the Korean War.

After the Korean War ended and due to the high cost of keeping them in service; starting in 1954 with Quincy, some of the Baltimores were decommissioned for good.

By 1969, only six ships were still in commission; five (Boston, Canberra, Chicago, Columbus, Albany) as CGs (guided missile cruisers), and only one unmodified ship, the Saint Paul, which remained active to serve in the Vietnam War, providing gunfire support.

Starting in 1972 all fourteen of the original Baltimores were sold for scrap after being decommissioned, with Chicago being the final one broken up in 1991.

In World War II, only the Canberra was damaged through enemy fire, when she was struck with an air-dropped torpedo on 13 October 1944, which killed 23 men in the engine room and left the ship immobilized.

A year later, repairs were completed at the Boston Naval Shipyard, and Canberra was assigned to the Atlantic Fleet.

The ship struggled through 70-knot (130 km/h; 81 mph) winds to Guam, where provisional repairs were made before sailing to the Puget Sound Naval Shipyard for a full reconstruction.

During the Korean War, a fire in a forward gun turret on 12 April 1952, killed 30 men on St. Paul.

They were designated the Boston class and returned to service in 1955 and 1956 respectively, reclassified as CAG-1 and CAG-2—"G" for "guided missile" and maintaining the "A" because they retained their heavy guns.

Because no high-caliber guns were retained, the Albany class ships received the designation CG rather than CAG.

The most conspicuous change was of course the addition of the missile-launching apparatus and its magazine of missiles, which took up the entire back half of the ship and replaced the guns which had been there.

The three Albanys were completely rebuilt from the deck level up; except for the hull, they bore very little resemblance to their former sister ships.

The original Baltimores could carry up to 2,250 long tons (2,290 t) of fuel, putting the maximum range at a cruising speed of 15 knots (28 km/h) at about 10,000 nautical miles (19,000 km).

After World War II the 20 mm anti-aircraft guns were removed without replacement, due to limited effectiveness against kamikaze attacks, and because it was expected they would be completely ineffective against postwar jet aircraft.

Four ships, Toledo, Macon, Helena, and Los Angeles, were also each equipped with three nuclear cruise missiles of the SSM-N-8 Regulus type between 1956 and 1958.

The radar systems were replaced in the Korean War with the more effective SPS-6 (built by Westinghouse Electric or later with the SPS-12 (from the Radio Corporation of America combined with an SPS-8 as a height-finder.

The onboard flight systems of the Baltimore-class cruisers during World War II consisted of two aircraft catapults on the side edges of the aft deck.

In the 1950s, the catapults and the accompanying capacity to launch airplanes were removed, though the cranes were left and the hangars used to house helicopters, ship's boats or the workings of the Regulus missile system.

Because of the helipad, the available firing angles for the main guns were sharply narrowed and the experiment was therefore quickly abandoned and not attempted on any other ships of the class.

The main differences between the two classes are the reduction to a single-trunked funnel; a redesigned forward superstructure that was placed 40 feet (12 m) further aft, primarily to decrease top-heaviness; and an increase in the arcs of fire for the guns.

The plans for the Saipan-class light aircraft carrier were adapted from the drafts of the Baltimore hull design, including the layout of the engines.

Because the Albany class was equipped almost exclusively for guided missiles, it required fewer crew than the Bostons and was roughly comparable numerically to the basic Baltimore.