The Des Moines-class cruisers were a trio of U.S. Navy (USN) heavy cruisers commissioned in 1948 and 1949. Largely based on the earlier Baltimore-class heavy cruisers, the Des Moines-class featured improved torpedo protection and heavier anti-aircraft armament. Relatively well-armored and protected, the class was unique in that it mounted nine of the world’s first auto-loading large-caliber guns, the 8-inch (203 mm) Mark 16 guns. These guns enabled Des Moines-class cruisers to fire two to three times faster than earlier 8 in guns with each barrel capable of 8-10 rounds per minute. They were the last of the “all-gun” heavy cruisers and were exceeded in size within the USN only by the 30,000-long-ton (30,481 t) Alaska-class "large cruisers" that straddled the line between heavy cruisers and battlecruisers. USS Des Moines (CA-134) and USS Salem (CA-139) were decommissioned by 1961 but USS Newport News (CA-148) served until 1975. Salem is a museum ship in Quincy, Massachusetts ; Des Moines and Newport News were scrapped.