History: American Civil War (1861-1865)

Despite compromises in 1820 and 1850, the slavery issues exploded in the 1850s. Lincoln did not propose federal laws against slavery where it already existed, but he had, in his 1858 House Divided Speech, expressed a desire to "arrest the further spread of it, and place it where the public mind shall rest in the belief that it is in the course of ultimate extinction." Much of the political battle in the 1850s focused on the expansion of slavery into the newly created territories. Both North and South assumed that if slavery could not expand it would wither and die.
Southern fears of losing control of the federal government to antislavery forces, and Northern resentment of the influence that the Slave Power already wielded in government, brought the crisis to a head in the late 1850s. Disagreements between Abolitionists and others over the morality of slavery, the scope of democracy and the economic merits of free labor versus slave plantations caused the Whig and "Know-Nothing" parties to collapse, and new ones to arise (the Free Soil Party in 1848, the Republicans in 1854, the Constitutional Union in 1860). In 1860, the last remaining national political party, the Democratic Party, split along sectional lines.
Northerners ranging from the abolitionist William Lloyd Garrison to the moderate Republican leader Lincoln emphasized Jefferson's declaration that all men are created equal. Lincoln mentioned this proposition many times, including his 1863 Gettysburg Address.
Almost all the inter-regional crises involved slavery, starting with debates on the three-fifths clause and a twenty-year extension of the African slave trade in the Constitutional Convention of 1787. The 1793 invention of the cotton gin by Eli Whitney increased by fiftyfold the quantity of cotton that could be processed in a day and greatly increased the demand for slave labor in the South. There was controversy over adding the slave state of Missouri to the Union that led to the Missouri Compromise of 1820. A gag rule prevented discussion in Congress of petitions for ending slavery from 1835–1844, while Manifest Destiny became an argument for gaining new territories, where slavery could expand. The acquisition of Texas as a slave state in 1845 along with territories won as a result of the Mexican–American War (1846–1848) resulted in the Compromise of 1850. The Wilmot Proviso was an attempt by Northern politicians to exclude slavery from the territories conquered from Mexico. The extremely popular antislavery novel Uncle Tom’s Cabin (1852) by Harriet Beecher Stowe greatly increased Northern opposition to the Fugitive Slave Law of 1850.