Slavery existed in the United States from 1619 until 1865, primarily in the Southern states. By 1860 there were nearly 4 million slaves out of a total US population of 12 million, most held by large plantation owners. Slaves endured cruel treatment and inhumane conditions, and an internal slave trade developed that forcibly relocated over 1 million slaves for economic reasons. Abolitionist movements led by figures like Douglass and Beecher Stowe grew in the Northern states, increasing sectional tensions, while the Dred Scott decision of 1857 upheld slavery. The system was finally abolished after the Union victory in the Civil War.