Beginning in 1846, Dred Scott sought freedom for himself and his slave family, contending that they gained that right when they lived temporarily in Illinois, a free state, and could not then be returned to slavery when they returned to Scott's former home in Missouri, a slave state.  In one of the most noted cases in American history, the U.S. Supreme Court in 1857 rejected this "once free, always free" doctrine, stating that slaves were not "citizens" entitled to the rights guaranteed in the U.S. Constitution.  The ruling sowed the seeds for years of bloody civil war and threatened preservation of the Union.