Pennsylvania class cruiser

Color-tinted postal card of USS Pennsylvania, circa 1905–1908
Class overview
Name:	Pennsylvania class
Builders:	William Cramp & Sons, Philadelphia Newport News Shipbuilding, Newport News, Virginia Union Iron Works, San Francisco
Operators:	United States Navy
Preceded by:	USS Brooklyn (ACR-3)
Succeeded by:	Tennessee class
Built:	1901–1908
In commission:	1905–1927
Completed:	6
Lost:	1
Scrapped:	5
General characteristics (as built)
Type:	Armored cruiser
Displacement:	13,680 long tons (13,900 t) (standard) 15,138 long tons (15,381 t) (full load)
Length:	504 ft (153.6 m)
Beam:	69 ft 6 in (21.2 m)
Draft:	26 ft 1 in (7.95 m)
Installed power:	16 × Babcock & Wilcox boilers (32 × Niclausse boilers in Pennsylvania and Colorado) 23,000 ihp (17,000 kW) (design)
Propulsion:	2 × vertical, inverted, triple-expansion engines 2 × screws
Speed:	22 kn (41 km/h; 25 mph)
Complement:	830
Armament:	4 × 8 in (203 mm)/40 caliber Mark 5 guns (2 × 2) 14 × 6 in (152 mm)/50 cal Mark 6 guns 18 × 3 in (76 mm)/50 cal rapid fire (RF) guns 12 × 3-pounder (47 mm (1.9 in)) RF guns 2 × 1-pounder (37 mm (1.5 in)) saluting guns 2 × 18 inch (450 mm) torpedo tubes
Armor:	Belt: 6–5 in (152–127 mm) Turrets: 6.5 in (165 mm) Deck: 4 in (102 mm) slope, 1.5 in (38 mm) flat Conning Tower: 9 in (229 mm)
General characteristics (1911)
Armament:	4 × 8 in/45 cal Mark 6 guns (2 × 2), remainder of armament unchanged
General characteristics (1919)
Armament:	4 × 8 in/45 caliber Mark 6 guns (2 × 2) 4 × 6 in/50 caliber Mark 6 guns 10 × 3 in/50 caliber RF guns 2 × 3 in/50 caliber anti-aircraft guns All 3-pounder guns removed

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 Pennsylvania class battleships. All of them 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 between 1930 and 1931 in accordance with the London Naval Treaty.

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 Tennessee-class 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". In 1906 the US Navy's battleships were concentrated in the Atlantic, and three or four armored cruisers were assigned to the Asiatic Fleet in the Philippines to counter Japan's rising naval power. By 1912 the rapid development of dreadnought battleships and battlecruisers left the armored cruisers unable to successfully engage the newer capital ships.

These ships were originally armed with four 8-inch (203 mm)/40 caliber Mark 5 guns in two twin turrets fore and aft. 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 6-inch (152 mm)/50 caliber Mark 6 guns were mounted in casemates on the sides. The large secondary armament, intended to combat torpedo boats, included eighteen 3-inch (76 mm)/50 caliber rapid fire (RF) guns and twelve 3-pounder (47 mm (1.9 in)) RF guns. Two 1-pounder (37 mm (1.5 in)) saluting guns and two 18-inch (457 mm) torpedo tubes were also carried.