Proslavery movement was an attempt by Southerners to justify and expand slavery in America between the 1830's and 1860. Southerners argued that both the Bible and history endorsed slavery, that emancipation (freeing the slaves) was impractical, and that slavery was necessary to save the Southern economy. John C. Calhoun and other well-known Americans defended slavery. They called it "the law of nature," "a positive good," and "the greatest and most admirable agent of civilization."