As a Quaker, Whittier was born into the Anti-Slavery cause. The Quakers had become the first organized religion to take a stand against slavery in 1688, in Germantown, PA. Their opposition to slavery remained strong through the 18th century, and by the 19th century they were playing a major role in the Underground Railroad. However, for Whittier it was more of a tradition than a personal cause until 1833, when Garrison asked him to find a place for an anti-slavery rally in Amesbury, Massachusetts, and Whittier not only found him a place but attended the meeting. That experience was to change his life. Shortly afterwards he responded to Garrison’s urging and joined the Anti-Slavery movement.
Today it is Whittier’s writing for the cause of abolition that is most remembered, but Whittier's activities in the cause of abolition were not limited to his writing. He helped to found the Liberty Party, its merger with the Free Soil Party, which ultimately became the base of the Republican Party that sent Lincoln to the White House. He assisted John Quincy Adams in his fight against curbs on free press or speech, badgered Clay and Webster on abolition rights, nagged his fellow poets to get more involved in the cause, and edited two anti-slavery papers: The Pennsylvania Freeman and the Middlesex Standard of Lowell, Massachusetts. He worked for John P. Hale, the first abolitionist senator, John C. Freemont, the presidential candidate for the Republican Party in 1856, and Charles Sumner, Massachusetts's anti-slavery senator. He went as a delegate to the first Anti-Slavery Convention and helped to draft the Declaration of the National Anti-slavery Convention. He had rocks and debris thrown at him in Concord, NH, rotten eggs in Newburyport, MA, and his office burned in Philadelphia. But it is for his poetry that he will be remembered.