Pennsylvania was invaded by the Confederate States Army three times: in 1862 during the War of Secession; from 1914 to 1917 during the Great War; and from 1942 to 1943 during the Second Great War. The first invasion led to the destruction of the Army of the Potomac, the fall of Philadelphia, the end of the War of Secession, and the international diplomatic recognition of the Confederate States. The latter two invasions were repelled by US forces at great cost. The Battle of Pittsburgh during the Second Great War was one of the critical battles of the war, as Confederate forces were routed and crushed.
The CSA used their first and only superbomb on Philadelphia in 1944. However, the bomb exploded on the outskirts of city west of the Schuylkill River and none of the main government buildings were effected.