Solomon Northup
Northup traveled through the United States making speeches about what happened to him.  He did this because he wanted voters to end slavery.  Northup wrote his speeches down as a book, 12 Years a Slave, and Derby published it in 1853.  Northup's book was published one year after Uncle Tom's Cabin by Harriet Beecher Stowe.  By then, people were saying that surely Beecher Stowe had only made up how bad slavery was.  Northup dedicated the book to Beecher Stowe.  He and Derby both said 12 Years a Slave helped prove that Beecher Stowe had not lied about slavery being bad.  They called it "Another Key to Uncle Tom's Cabin."