By 1850, Americans recognized the divisions that questions about slavery in the territories had caused, but few expected those divisions would lead to a crisis of union by 1860. However, that was precisely what happened. Throughout the 1850s, sectional tensions mounted. Increasingly, northerners and southerners concluded they had little in common. Northerners saw the extension of slavery into the territories as a threat to their way of life based on the principles of free labor. Southerners, however, thought they needed to expand slavery to preserve their way of life built on the institution of slavery. When California applied to the Union as a free state, both sides felt compelled to press their interests at the national level. The Compromise of 1850 resolved the question of California’s status, though it hardly lessened the tensions.
Questions about slavery in Kansas only reinvigorated the debate. After 1854, southerners sought federal protection of slavery. The Dred Scott decision seemingly gave them that protection. As northerners embraced the antislavery positions of the new Republican Party, they refused to accept the legitimacy of the Supreme Court’s ruling. John Brown’s raid on Harper’s Ferry in 1859 convinced southerners that northerners would go to any lengths to abolish slavery. Therefore, Abraham Lincoln’s victory in the presidential election of 1860 prompted the secession of the lower South and the creation of the Confederate States of America.