states of Ohio, Michigan, Indiana, Illinois, Wisconsin and part of Minnesota) doubled the size of the United States. In the decades leading up to the Civil 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 the Puritans and Puritan values over a thousand times. Parker, in urging New England congressmen to support the abolition of slavery, wrote, "The son of the Puritan . . . is sent to Congress to stand up for Truth and Right." Literature served as a means to spread the message to common folks. Key works included Twelve Years a Slave, the Narrative of the Life of Frederick Douglass, 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. A more unusual abolitionist than those named above was Hinton Rowan Helper, whose 1857 book, The Impending Crisis of the South: How to Meet It, "[e]ven more perhaps than Uncle Tom's Cabin ... fed the fires of sectional controversy leading up to the Civil War." A Southerner and a virulent racist, Helper was nevertheless an abolitionist because he believed, and showed with statistics, that slavery "impeded the progress and prosperity of the South, ... dwindled our commerce, and other similar pursuits, into the most contemptible insignificance; sunk a large majority of our people in galling poverty and ignorance, ... [and] entailed upon us a humiliating dependence on the Free States...." By 1840 more than 15,000 people were members of abolitionist societies in the United States. Abolitionism in the United States became a popular expression of moralism, and led directly to the Civil War. In churches, conventions and newspapers, reformers promoted an absolute and immediate rejection of slavery. Support for abolition among the religious was not universal though. As the war approached, even the main denominations split along political lines, forming rival Southern and Northern churches. For example, in 1845 the Baptists split into the Northern Baptists and Southern Baptists over the issue of slavery. Abolitionist sentiment was not strictly religious or moral in origin. The Whig Party became increasingly opposed to slavery because it saw it as inherently against the ideals of capitalism and the free market. Whig leader William H. Seward (who would serve as Lincoln's secretary