Prior to and during the Civil War , Pennsylvania was a divided state . Although Pennsylvania had outlawed slavery , many conservative Pennsylvanians believed that the federal government should not interfere with the institution of slavery . One such individual was Democrat James Buchanan , the last pre-Civil War president . Buchanan 's party had generally won presidential and gubernatorial elections in Pennsylvania . However , the nascent Republican Party 's first convention took place in Philadelphia , and the 1860 elections saw the Republican Party win the state 's presidential vote and the governor 's office . After the failure of the Crittenden Compromise , the secession of the South , and the Battle of Fort Sumter , the Civil War began with Pennsylvania as a key member of the Union . Despite the Republican victory the 1860 election , Democrats remained powerful in the state , and several " copperheads " called for peace during the war . The Democrats re-took control of the state legislature in the 1862 election , but incumbent Republican Governor Andrew Curtin retained control of the governorship in 1863 . In the 1864 election , President Lincoln narrowly defeated Pennsylvania native George B. McClellan for the state 's electoral votes
first convention
1856 Republican National Convention
History of Pennsylvania