Slavery/ Missouri compromise: South utilized slaves to tend its large plantations and perform other duties. Additional territories gained from the U.S.–Mexican War of 1846–1848 heightened the slavery debate. Abolitionists fought to have slavery declared illegal in those territories, as the Northwest Ordinance of 1787 had done in the territory that became the states of Ohio, Indiana, Illinois, Michigan and Wisconsin.
State rights: States’ Rights refers To the struggle between the federal government and individual states over political power. In the Civil War era, this struggle focused heavily on the institution of slavery and whether the federal government had the right to regulate or even abolish slavery within an individual state. The sides of this debate were largely drawn between northern and southern states, thus widened the growing divide within the nation.
Abraham Lincoln: When the Republican candidate Abraham Lincoln won the 1860 presidential election, Southern fears that the Republicans would abolish slavery reached a new peak. Lincoln was an avowed opponent of the expansion of slavery but said he would not interfere with it where it existed.
Underground Railroad: abolitionists actively helped runaway slaves to escape via “the Underground Railroad,” and there were instances in which men, even lawmen, sent to retrieve runaways were attacked and beaten by abolitionist mobs. To the slave holding states, this meant Northerners wanted to choose which parts of the Constitution they would enforce, while expecting the South to honor the entire document