In the United States, abolitionism, the movement that sought to end slavery in the country, was active from the late colonial era until the American Civil War, the end of which brought about the abolition of American slavery through the Thirteenth Amendment to the United States Constitution (ratified 1865).

The anti-slavery movement originated during the Age of Enlightenment, focused on ending the trans-Atlantic slave trade. In Colonial America, a few German Quakers issued the 1688 Germantown Quaker Petition Against Slavery, which marks the beginning of the American abolitionist movement. Before the Revolutionary War, evangelical colonists were the primary advocates for the opposition to slavery and the slave trade, doing so on humanitarian grounds. James Oglethorpe, the founder of the colony of Georgia, originally tried to prohibit slavery upon its founding, a decision that was eventually reversed.

During the Revolutionary era, all states abolished the international slave trade, but South Carolina reversed its decision. Acting as soon as the Constitution allowed, in 1807 Congress made the importation of slaves a crime. From the Revolutionary War to 1804, all Northern states abolished slavery either immediately or gradually. No Southern state did so. Immediate emancipation became a war goal for the Union in 1862 and was fully achieved in 1865.