In Indiana County, early settlement by Scottish-Irish Presbyterians with their own history of persecution laid the grounds for vibrant anti-slavery sentiment in the decades before the Civil War. In addition, by the mid 1840's, there were at least two African Methodist Episcopal Zion congregations whose mission was to "aid refugees." Other denominations like the Wesleyan Methodists and the Baptists were opposed to slavery as well.
In 1850, another major compromise over slavery saved the Union but caused a reign of terror for people of African descent. Free people, on the word of a white man, could be plucked off the street and sold into slavery. In Blairsville and Indiana, anti-slavery mobs rescued fugitive slaves and whole families throughout the county were active in the Underground Railroad. Indiana County became known as a "hotbed of abolition" and to fugitive slaves as a welcoming haven. Clashes between slavecatchers and locals were reported in newspapers all over the country.
The 1850 Compromise also introduced the concept of popular sovereignty. People in the territories would vote to be free or slave and determine "democratically" how to enter the Union. One great test of this principle took place over the settlement of Kansas. Pro- and anti-slavery settlers packed their wagons and went west. The Plumville Baptist Church sponsored the Pennsylvania-Kansas Liberty Society which raised money and provisions to send local settlers to build a free Kansas.
In the battles that ensued, two Indiana County men died. One was the pacifist son of Dr. Robert Mitchell, who had been convicted and fined heavily for violating Fugitive Slave Laws. John Mitchell volunteered to go for provisions after pro-slavery Border Ruffians sacked Lawrence. But he refused to carry a gun. He was captured, tortured and thrown into prison where he caught pneumonia and died. Another Indiana County man, Albert Hazlett, joined John Brown in Kansas and died on the scaffold after Brown's failed slave insurrection at Harper's Ferry, Virginia in 1859.
Out of Bleeding Kansas came the Republican Party, whose primary tenet was to stop the expansion of slavery, and by containing it, to kill it. Republicans advocated industry, expansion, free soil, free labor, and social reform. In Indiana County, 4/5 of the Republican platform was about slavery. Democrats supported the status quo and opposed agitation on the slavery issue. In the election of 1860, Republican Abraham Lincoln won Indiana County with 3910 votes, versus 1369 votes for all other candidates combined. In response to Lincoln's election, South Carolina seceded from the Union.