Born in Southampton, Virginia, Dred Scott's first name was simply "Sam." He worked as a farmhand, handyman and stevedore. He moved with his master to Huntsville, Alabama, and later to St. Louis, Missouri. In 1831 his owner, Peter Blow, died and John Emerson, a surgeon in the U.S. Army, bought him. Sam accompanied his new master to Illinois (a free state) and Wisconsin (a territory). Sometime after 1836 he received permission to marry and by 1848 he had changed his name to Dred Scott. At various times he attempted to buy his freedom or escape but was unsuccessful. In 1843 Emerson died and left his estate to his widow Irene Emerson, who also refused Scott his freedom. He then obtained the assistance of two attorneys who helped him to sue for his freedom in county court.
Scott lost this case, but the verdict was set aside and, in 1847, he won a second trial on the grounds that his slave status had been nullified upon entering into a free state. Scott received financial backing and legal representation through the sons of Peter Blow, Irene Emerson's brother John Sanford and her second husband Dr. C. C. Chaffee, all of whom apparently saw the case as an important challenge to slavery. In 1857 the United States Supreme Court ruled against Scott, stating that slaves were not legally citizens of the United States and therefore had no standing in the courts. Shortly after the decision was handed down Mrs. Emerson freed Scott. The case led to the nullification of the Missouri Compromise of 1820, allowing the expansion of slavery into formerly free territories and strengthening the abolition movement.