Emancipation Proclamation: This was an executive order issued by President Abraham Lincoln in 1862 that declared all slaves in Confederate-held territory free (although it didn't immediately end slavery everywhere).
Underground Railroad: A network of secret routes and safe houses used by enslaved African Americans to escape into free states and Canada with the aid of abolitionists who were sympathetic to their cause.
Frederick Douglass: An escaped slave who became a prominent activist, author, and public speaker. He became a leader in the abolitionist movement, which sought to end the practice of slavery before and during the Civil War.