Liberty party, in U.S. history, an antislavery political organization founded in 1840. It was formed by those abolitionists, under the leadership of James G. Birney and Gerrit Smith, who repudiated William Lloyd Garrison's nonpolitical stand. Birney, their presidential candidate in 1840, received a little more than 7,000 votes. Because of better local organization and the issue of the annexation of Texas, he polled more than 60,000 votes in 1844, drawing enough support away from Henry Clay in New York state to throw the presidency to James K. Polk. The party remained strong in local elections in 1846, but in 1848 it withdrew its nominee, John P. Hale, and united with antislavery Whigs and Democrats to form the stronger Free-Soil party.
See T. C. Smith, The Liberty and Free Soil Parties in the Northwest (1897, repr. 1967).