(1799 – September 17, 1858), was an African-American slave in the United States who sued unsuccessfully for his freedom in the Dred Scott v. Sandford case of 1857. His case was based on the fact that although he and his wife Harriet Scott were slaves, he had lived with his master Dr. John Emerson in states and territories where slavery was illegal according to both state laws and the Northwest Ordinance of 1787, including Illinois and Minnesota (which was then part of the Wisconsin Territory). The United States Supreme Court ruled seven to two against Scott, finding that neither he, nor any person of African ancestry, could claim citizenship in the United States, and therefore Scott could not bring suit in federal court under diversity of citizenship rules. Moreover, Scott's temporary residence outside Missouri did not bring about his emancipation under the Missouri Compromise, since that would improperly deprive Scott's owner of his legal property.
The case raised the issue of a slave who had lived in a free state. Congress had not asserted whether slaves were free if they set foot upon free soil. The ruling overturned the Missouri Compromise since by the court's logic, any attempt at regulating slavery in the federal Territories deprived a slave owner of his property without due process. This enraged the abolitionist Republicans and further exacerbated sectional sentiments that led to the Civil War.
Scott had traveled with his master Dr. John Emerson, who was in the US Army and often transferred. Scott's extended stay with his master in Illinois, a free state, gave him the legal standing to make a claim for freedom, as did his extended stay at Fort Snelling in the Wisconsin Territory (now Minnesota), where slavery was also prohibited. But Scott did not file a petition for freedom while living in the free lands—perhaps because he was unaware of his rights at the time, or because he was fearful of possible repercussions. After two years, the army transferred Emerson to territory where slavery was legal: first to St. Louis, Missouri, then to Louisiana. In just over a year, the recently married Emerson summoned his slave couple. Instead of staying in the free territory of Wisconsin (now Minnesota), or going to the free state of Illinois, the two traveled nearly 1,250 miles (2000 km), apparently unaccompanied, down the Mississippi River to meet their master. Only after Emerson's death in 1843, when Emerson's widow hired out Scott to an army captain, did Scott seek freedom for himself and his wife. First he offered to buy his freedom from Emerson's widow, Irene Emerson—then living in St. Louis—for US $300, about $7,000 in current value. After she refused his request, Scott sought freedom in the St. Louis Circuit Court.