The major cause of the conflict between the North and South in America during the Civil War was slavery and its expansion into new territories. The southern economy heavily relied on slave labor, while the North was increasingly industrialized and favored free labor. Disputes over whether new states should be free or slave-holding created deep divisions. The Missouri Compromise and the Compromise of 1850 attempted to address these tensions, but failed to provide lasting solutions. Ultimately, the election of Abraham Lincoln in 1860, who opposed the spread of slavery, triggered the secession of southern states.