In the decades leading up to the war, abolitionists, such as Theodore Parker, Ralph Waldo Emerson, Henry David Thoreau, and Frederick Douglass, repeatedly used the Puritan heritage of the country to bolster their cause. The most radical anti-slavery newspaper, The Liberator, invoked Puritan values over a thousand times. Parker, in urging New England congressmen to support slavery's abolition, wrote, "The son of the Puritan ... is sent to Congress to stand up for Truth and Right." Literature spread the message; key works included Twelve Years a Slave, the , American Slavery as It Is, and the most important: Uncle Tom's Cabin, the best-selling book of the 19th century, aside from the Bible.