In 1815, while living at Saint Clairsville, Ohio, he organized an antislavery association, known as the "Union Humane Society," which within a few months had a membership of more than five hundred men.
He was bitterly denounced by slaveholders and also by such non-slaveholders as disapproved of all antislavery agitation, and in January 1827 he was assaulted and seriously injured by a slave-trader, Austin Woolfolk, whom he had severely criticized in his paper.
He was essentially humane; and it is worthy of notice that he was in favour of the abolition of slavery, while humane men like his friend Lord Sheffield, Dr Johnson and Boswell were opposed to the antislavery movement.
The settlers who had flocked to California after the discovery of gold in 1848 adopted an antislavery state constitution on the 13th of October 1849, and applied for admission into the Union.
His tariff and antislavery views, moreover, carried him more and more away from the Democratic party and toward the Whigs.
The ends being political, so also, thought Birney, must be the means; as parties in the south were fusing, he laboured to re-align parties in the north, and advocated the formation of an independent antislavery party.
Bismarck, by summoning a conference to Berlin (1884-1885) to discuss African questions, secured for Germany a European recognition which was very grateful to the colonial parties; and in 1888, by lending his support to the antislavery movement of Cardinal Lavigerie, he won the support of the Centre, who had hitherto opposed the colonial policy.
These differences led to the organization of a new National AntiSlavery Society in 1840, and to the formation of the "Liberty Party" (q.v.) in politics.
For several years preceding the Civil War it was a station on the "underground railway" and the headquarters of "the Western Anti-Slavery Society," which published here the AntiSlavery Bugle.
He was elected to the national house of representatives as an antislavery Whig in 1854, soon afterwards joining the new Republican party, and served in the house from 1855 until 1867.
He became an abolitionist in 1835, after seeing an antislavery meeting at Utica broken up by a mob.