The oldest of 13 children born to Harriet and Abraham Shadd, leaders of the free black community who were active in the Underground Railroad, Mary Ann Shadd understood at an early age the importance of racial equality. Because Delaware was a slave state and forbade the education of blacks, Shadd was sent to a Quaker school in West Chester, Penn. Returning to Delaware as a teacher, the 16-year-old took a post ministering to less fortunate African Americans. In response to the Fugitive Slave Act of 1850, Shadd published a pamphlet, "A Plea for Emigration or Notes of Canada West," which espoused emigration to Canada; Shadd herself moved north in 1851. Now living in Chatham, Canada, Shadd established her own newspaper, Provincial Freeman, which endorsed racial and sexual equality. In 1856, she married Thomas F. Cary with whom she had one daughter, Sally (Thomas died in 1860). Shadd Cary later moved to Washington D.C., where she helped recruit for the Union Army and opened a school for African American children. She attended Howard University Law School, graduated in 1870, and became the first African American female lawyer. As a lawyer, she focused on fighting for women's rights, including their right to vote.
Shadd Cary met John Brown in 1858. Impressed with Brown's militant abolitionism, she published Voice from Harper's Ferry, based on the notes of Osborne P. Anderson, the sole survivor of John Brown's raid on the federal arsenal at Harper's Ferry, Va.