Anthony belonged to a Quaker community that devoted itself to eliminating slavery. Along with many of their friends, the Anthony family provided safety and shelter to runaway slaves and helped them on their journey.

Beginning in the 1850s, Anthony began giving speeches against slavery. For several years she was the head of the New York Antislavery Association. During the American Civil War (1861-1865), she helped to form the Women’s National Loyal League that gathered 400,000 petitions against slavery and sent them to Congress. These groups pressured Congress and eventually resulted in the passage of  the 13th, 14th, and 15th amendments to the U.S. Constitution.