Named for the Commonwealth of Pennsylvania, she was laid down at the Newport News Shipbuilding and Drydock Company in October 1913, was launched in March 1915, and was commissioned in June 1916.

During the Philippines campaign, in addition to her typical shore bombardment duties, she took part in the Battle of Surigao Strait, though due to her inadequate radar, she was unable to locate a target and did not fire.

At full capacity, the ship could steam at a speed of 12 knots (22 km/h; 14 mph) for an estimated 7,552 nautical miles (13,990 km; 8,690 mi) with a clean bottom.

Pennsylvania then began sea trials in 20 July, steaming first to the southern drill grounds off the Virginia Capes and then north to the coast of New England.

After emerging from the shipyard in January 1917, she steamed south to join fleet exercises in the Caribbean Sea, during which she stopped in: Culebra, Puerto Rico; Santo Domingo, Dominican Republic; and Port-au-Prince, Haiti.

The ships visited several ports in the Caribbean, including in the US Virgin Islands and Puerto Rico before returning to the Pacific in early April.

She received a number of modifications, including increased deck and turret roof armor, anti-torpedo bulges, new turbo-generators, new turbines, and six new three-drum boilers.

The ship left the shipyard on 16 October and returned to San Francisco two days later, beginning a period of cruises off the coast of California and visits to cities in the state.

Another period in San Pedro followed until 20 June, after which she embarked on a two-month cruise along the west coast that concluded with another stay at Puget Sound on 28 September.

Fleet Problem XXII was scheduled for January 1941, but the widening of World War II by this time led the naval command to cancel the exercises.

When it became clear that the port was under air attack from the Japanese fleet, Pennsylvania's crew rushed to their battle stations, and between 08:02 and 08:05, her anti-aircraft gunners began engaging the hostile aircraft.

Pennsylvania's anti-aircraft gunners fired at all of these aircraft but failed to hit any of them, apparently owing to incorrect fuse settings that caused the shells to explode before they reached the correct altitude.

Ten minutes later, the destroyers began to explode as the fires spread to ammunition magazines, and at 09:41, Downes was shattered by an explosion that scattered parts of the ship around the area.

As part of her crew battled the fire in her bow, other men used the ship's boats to ferry anti-aircraft ammunition from stores in the West Loch of Pearl Harbor.

Further training followed in March, and from 14 April to 1 August, she took part in extensive maneuvers off the coast of California;[11] during this period, she underwent an overhaul at the Mare Island Naval Shipyard in San Francisco.

The Catalina radioed Pennsylvania, which took evasive maneuvers and escaped unharmed; a pair of destroyers then spent the next ten hours hunting the submarine before severely damaging her and forcing her to surface.

She was forced to leave Adak on 21 May for repairs at Puget Sound that lasted from 31 May to 15 June; during the overhaul, another accidental explosion killed one man and injured a second.

Early on the morning of 24 November, the ship was rocked by an explosion off her starboard bow; lookouts reported that the escort carrier Liscome Bay had been torpedoed and had exploded.

While en route that night, one of the escorting destroyers reported a sonar contact and the ships of the fleet took evasive maneuvers; in the darkness, Pennsylvania accidentally collided with the troop transport Talbot.

Pennsylvania left on 12 October in company with the battleships Mississippi, Tennessee, California, Maryland, and West Virginia, under the command of Rear Admiral Jesse B. Oldendorf.

They arrived off Leyte on 18 October and took up bombardment positions; over the next four days, they covered Underwater Demolition Teams, beach reconnaissance operations, and minesweepers clearing the way for the landing force.

[11] On 24 October, reports of Japanese naval forces approaching the area led Oldendorf's ships to prepare for action at the exit of the Surigao Strait.

Yamashiro was set on fire and then exploded; she turned to flee, covered by a salvo of torpedoes from the burning Mogami, but the American battleships were able to evade them without damage.

[16] Shima's ships passed the still-floating Fusō and realized that Nishimura had entered a trap, so he reversed course to flee; in the confusion, his flagship Nachi collided with Mogami, damaging her and slowing her to be attacked by American light forces.

The ship remained on station off Leyte until 25 November, when she departed for Manus, from which she steamed to Kossol Roads off Palau on 15 December to refill her magazines.

She conducted gunnery training on 22 December, and on 1 January 1945, Pennsylvania re-joined Oldendorf's Fire Support Group on the way to Lingayen Gulf for the next major operation in the Philippines.

With the kamikaze threat in mind, her anti-aircraft armament was increased to seventy-one 20 mm guns in twenty-seven single and twenty-two twin mounts.

The torpedo opened a hole approximately 30 ft (9.1 m) in diameter, causing the ship to take on a considerable amount of water and begin to settle by the stern.

The next day, she was taken into a floating drydock, where a large steel patch was welded over the torpedo hole, which would allow the ship to make the voyage back for permanent repairs.

[11] On 16 January 1946, Pennsylvania was designated to be expended as a target ship for the Operation Crossroads atomic bomb tests at Bikini Atoll to be carried out later that year.