300px|thumb|right|USS South Dakota with a cage foremast, circa 1911–1916
The Pennsylvania class of six armored cruisers served in the United States Navy from 1905 to 1927. All six were renamed for cities 1912–1920, to make the state names available for the new battleships beginning with the s. All of these served during World War I, with California (then San Diego) being the only ship of the class to be lost. The remaining five armored cruisers were scrapped in 1930 and 1931 in accordance with the London Naval Treaty.
Design and construction
These ships were ordered in fiscal years 1900 (ACR-4 to ACR-6) and 1901 (ACR-7 to ACR-9) as part of the naval buildup touched off by the Spanish–American War. Together with the four immediately succeeding ships they were called the "Big Ten". They were originally intended to operate in the battle line with battleships. However, their role was changing even as they entered service. The 1904 report of the Navy's Bureau of Navigation, examining the results of the Russo-Japanese War, noted that "...the work of the armored cruisers was auxiliary to that of the battleships..." and "They can serve with battleships, but they can never take their place". However, these were replaced with 8-inch/45 caliber Mark 6 guns by 1911 as a result of a gun bursting on Colorado in 1907. Fourteen /50 caliber Mark 6 guns were mounted in casemates on the sides. The large secondary armament, intended to combat torpedo boats, included eighteen /50 caliber rapid fire (RF) guns and twelve 3-pounder () RF guns. Two 1-pounder () saluting guns and two torpedo tubes were also carried. However, the official Ships' Data Book series indicates that by 1921 all of the 6-inch guns were remounted, only to be dismounted again by 1929. In 1922, Pittsburghs forward funnel and the associated boilers were removed, leaving her with 12 Babcock & Wilcox boilers. This is said to be the first action in World War I that resulted in the award of the Medal of Honor. San Diego was sunk on 19 July 1918, probably by a mine laid by off Fire Island, New York.
Ships in class
The six ships of the Pennsylvania class were: