They both were active political figures during the 19th century that fought for the rights of African-Americans and women.
Frederick Douglass (1818-1895) was a politician, abolitionist, and writer. He was a black famous orator in the 1800s that escaped from slavery in Maryland. His writings are important sources to understand America in the 1800s.
Sojourner Truth (c. 1797-1883) was an important abolitionist and women's rights activist. She escaped slavery with her daughter in 1826 and in 1828 was the first black woman to win in Court a son back from a white man. She is also the author of the "Ain't I a woman?" which criticizes feminists' ignorance about the life of black women.
William Lloyd Garrison (1805-1879) was a white abolitionist and journalist. He was editor of the famous newspaper The Liberator.