Abolitionism was a movement to end the institution of slavery. In the colonial and revolutionary periods, abolitionism in America was characterized by a focus on gradual emancipation via specific, limited measures such as curbing the African slave trade and emancipating enslaved children. Prior to the American Revolution, only the Society of Friends, or Quakers, consistently advocated for abolition on moral grounds, as they believed that all human beings were fundamentally equal before God. The Quakers' moral perspective, as well as the Enlightenment and the American Revolution's emphasis upon freedom and rejection of arbitrary rule, were influential sources for early American abolitionist thought. Yet even as gradualism prevailed in the North and the institution of slavery waned there in the post-revolutionary period, slavery grew more entrenched in the U.S. South. From American Independence until the 1830s, most American anti-slavery agitation was centered in the South, and in both North and South most abolitionist work was connected with the American Colonization Society. In the decades prior to the Civil War, however, American abolitionism shifted North.

White Northern missionaries, frustrated with the American Colonization Society's ambiguity on the question of emancipation and desiring greater attention to the stark moral implications of slavery, began to reject gradualism and demand immediate, uncompensated emancipation. Lacking direct experience with the institution of slavery, this new wave of abolitionists framed slavery as a peculiar Southern institution and sin. Abolitionist rhetoric grew both more stark and abstract, and abolitionists such as William Lloyd Garrison began to use "slavery" as a metaphor for many kinds of exploitation. The Liberty Party was one political organization that grew out of the new immediatist abolitionism, although its success lay more in spreading ideas than in political change or reform. Most Northern abolitionist organizations were not integrated, and some Black Abolitionists—such as Theodore Wright, Charles Ray, Samuel Cornish, and Frederick Douglass—increasingly pressed for separatist and integrated abolitionist organizations.

Immediatist abolitionism inadvertently contributed to heightened tensions between the North and South, as influential elements in the South incorrectly assumed and charged that Northern public opinion was dominated by immediatist thought. The assumed association between any anti-slavery sentiment and radical immediatist abolitionism ultimately convinced many Southerners that Abraham Lincoln was unacceptable as president, even though Lincoln was, in reality, a pragmatic gradualist rather than a radical immediatist. Although Lincoln viewed slavery as a social, political, and moral evil, as president he prioritized national unity over abolitionism and only advocated emancipation when it advanced federal military and political interests. The 1863 Emancipation Proclamation was, to Lincoln, a wartime instrument for victory rather than an urgent moral necessity. It was not until the Thirteenth Amendment to the U.S. Constitution was ratified in December 1865 that slavery was finally abolished in the United States.

Lawrence J. Friedman, "Abolitionism," Dictionary of Afro-American Slavery, ed. by Randall M. Miller and John David Smith (Westport, CT: Praeger, Oxford University Press, 1999), 1-7; Martin A. Klein, Historical Dictionary of Slavery and Abolition, 2nd ed. (New York: Rowman and Littlefield, 2014), 31-32; James Oakes, The Crooked Path to Abolition: Abraham Lincoln and the Antislavery Constitution (New York: W. W. Norton, 2021), xii-xiv, 186-91, 204; Eric Foner, The Fiery Trial: Abraham Lincoln and American Slavery (New York: W. W. Norton, 2010), 240-44, 312-16.