History: American Civil War (1861-1865)

Nationalism was a powerful force in the early 19th century, with famous spokesmen like Andrew Jackson and Daniel Webster. While practically all Northerners supported the Union, Southerners were split between those loyal to the entire United States (called "unionists") and those loyal primarily to the southern region and then the Confederacy. C. Vann Woodward said of the latter group, "A great slave society...had grown up and miraculously flourished in the heart of a thoroughly bourgeois and partly puritanical republic. It had renounced its bourgeois origins and elaborated and painfully rationalized its institutional, legal, metaphysical, and religious defenses....When the crisis came it chose to fight. It proved to be the death struggle of a society, which went down in ruins." Insults to Southern national honor included Uncle Tom's Cabin (1854) and John Brown in 1859.
States' rights
Everyone agreed that states had certain rights—but did those rights carry over when a citizen left that state? The Southern position was that citizens of every state had the right to take their property anywhere in the U.S. and not have it taken away—specifically they could bring their slaves anywhere and they would remain slaves. Northerners rejected this "right" because it would violate the right of a free state to outlaw slavery within its borders. Republicans committed to ending the expansion of slavery were among those opposed to any such right to bring slaves and slavery into the free states and territories. The Dred Scott Supreme Court decision of 1857 bolstered the Southern case within territories, and angered the North.