History: American Civil War (1861-1865)

The Abolitionist movement in the United States had roots in the Declaration of Independence. Slavery was banned in the Northwest Territory with the Northwest Ordinance of 1787. By 1804 all the Northern states had passed laws to abolish slavery. Congress banned the African slave-trade in 1808, although slavery grew in new states in the deep south. The Union was divided along the Mason Dixon Line into the North (free of slaves), and the South, where slavery remained legal.
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.