Fourteen Baltimore s were completed, more than any other class of heavy cruiser the British County class had 15 vessels planned, but only 13 completed , along with another three ships of the Oregon City sub-class. Fast and heavily armed, the Baltimore cruisers were mainly used in World War II as anti-aircraft cruisers to protect the fast aircraft carriers in battle groups from air attack. Additionally, their 8-inch mm main guns and secondary 5-inch mm guns were regularly used to bombard land targets in support of amphibious landings.
After the war, only six Baltimore s 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. Except for St. Paul , all the ships retaining all-gun configurations had very short 18 years or less service lives, and by were decommissioned , and started being sold for scrap. However, four Baltimore -class cruisers were refitted and converted into some of the first guided missile cruisers in the world, becoming two of the three Albany -class and two Boston -class cruisers.
The last of these was decommissioned in , with the Chicago lasting until in reserve. No example of the Baltimore class still exists. Immediately after the outbreak of World War II in September , the US Navy initiated studies regarding a new class of heavy cruiser that led to construction of the Baltimore class.
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.
It was also based partly on the Cleveland class , a light cruiser that was then being built. In profile, the Baltimore s looked very much like the Cleveland -class light cruisers, the obvious difference being that the larger Baltimore s carried nine 8-inch mm guns in three triple turrets, compared to the twelve 6-inch mm guns in four triple turrets of the Cleveland s. The construction of the first four ships of the Baltimore class began on 1 July , and four more were ordered before the year was out.
