American Anti-Slavery Society, association organized in December 1833 in Philadelphia to advance the abolition of slavery in the United States. It was established by delegates from similar state and local societies, including the Boston organization, which had been founded in January 1832 under the leadership of the abolitionist William Lloyd Garrison and was the first such society in America. The three abolitionist leaders responsible for establishing the American Anti-Slavery Society were Theodore Dwight Weld, Arthur Tappan, and Lewis Tappan. Militant in the fight against slavery, the organizers were regarded in the South as fanatics; members of the society were denounced, and meetings were broken up. In 1839 some less-militant members broke away from the society and formed the Liberty Party. The society operated until 1870, when the adoption of the 15th Amendment to the U.S. Constitution secured the right to vote for blacks.