Leaders of the antislavery movement included journalist William Lloyd Garrison (1805–1879), founder of the influential antislavery journal The Liberator and of the American Anti-Slavery Society (established 1833); brothers Arthur (1786–1865) and Lewis (1788–1873) Tappan, prominent New York merchants who were also founders of the American Anti-Slavery Society; and Theodore Dwight Weld (1803–1895), leader of student protests, organizer of the American and Foreign Anti-Slavery Society, and author of The Bible Against Slavery (1837) and other abolitionist works.

Underground Railroad conductor Harriet Tubman (c. 1820–1913) worked against slavery by helping to free hundreds of blacks who escaped slavery in the South, heading for northern states and Canada. Writers such as Harriet Beecher Stowe (1811–1896), author of Uncle Tom’s Cabin (1851–52), helped strengthen the abolitionist cause and were instrumental in swaying public sentiment. In the hands of some activists, the movement became violent: In 1859 ardent abolitionist John Brown (1800–1859) led a raid on the armory at Harpers Ferry (in present-day West Virginia), which proved a failed attempt to emancipate slaves by force.