USS Pennsylvania, lead ship of a class of two 31,400-ton battleships, was built at Newport News, Virginia. Commissioned in June 1916, she served as the Atlantic Fleet's flagship into the early "Twenties". Though her operations during this time were primarily off the U.S. east coast and in the Caribbean area, Pennsylvania briefly cruised to France in December 1918. Transiting the Panama Canal to the Pacific early in 1921, she became flagship of the newly-organized Battle Fleet. During the next eight years, she led the Navy's battleships in maneuvers in the Atlantic, Caribbean and in the Pacific, including a cruise to Australia and New Zealand in mid-1925.
From June 1929 to May 1931, Pennsylvania received an extensive modernization at the Philadelphia Navy Yard, Pennsylvania. She emerged with new "tripod" masts, improved combat systems, and an enlarged armored conning tower to better support her mission as fleet flagship. Through the following decade, Pennsylvania continued her pattern of drills, at-sea exercises and periodic major "Fleet Problems" conducted to refine the Navy's war plans.
When Japan attacked on 7 December 1941, Pennsylvania, flagship of the United States Fleet, was in drydock at the Pearl Harbor Navy Yard. Her relatively light damage was repaired over the next few months, and she operated along the U.S. west coast and off Hawaii until October 1942. Following an overhaul that significantly updated her secondary battery of 5" guns and added many anti-aircraft machine guns, Pennsylvania went to Alaskan waters, where she participated in the recapture of Attu in May 1943 and Kiska in August.
In November 1943, Pennsylvania bombarded Makin during the amphibious assault on the Gilbert Islands. She repeated this role a few months later at Kwajalein and Eniwetok, and in June and July 1944 at Saipan, Tinian and Guam. Her guns supported landings in the Palaus in September 1944 and at Leyte in October. When the Japanese Navy responded vigorously to the latter operation, Pennsylvania helped to destroy part of the enemy fleet in the Battle of Surigao Strait.
In January 1945, Pennsylvania took part in the Lingayen Gulf invasion. Freshly returned to the combat zone after another overhaul, she was seriously damaged by a Japanese aerial torpedo off Okinawa on 12 August 1945, the last major Navy ship to be hit during the Second World War. Too old for retention in the post-war fleet, Pennsylvania was repaired only enough to fit her for target duty. She served in that capacity during the July 1946 Bikini atomic bomb tests. Subsequently moored at Kwajalein for studies of residual radioactivity, USS Pennsylvania was scuttled at sea on 19 February 1948.