"The question is simply this: Can a negro, whose ancestors were imported into this country, and sold as slaves, become a member of the political community formed and brought into existence by the Constitution of the United States, and as such become entitled to all the rights, and privileges, and immunities, guarantied by that instrument to the citizen? " (Dred Scott v. Sanford)
Dred Scott was an unlikely candidate to become the impetus and rallying cry of a brand-new political party in the mid-19th century. Born into slavery in Virginia as Sam Scott, the young slave took the name of his older brother, Dred, after Dred's death. He moved throughout Southern slave states as property of the Blow family until he was sold to US Army doctor John Emerson in St. Louis, Missouri. Emerson's commission in the army eventually brought him to the Wisconsin Territory in 1836, which was north of the line established by the Missouri Compromise of 1820 and was thus free territory where slavery was illegal. Naturally Emerson brought his slaves along with him, and Dred Scott lived for an extended period of time in free territory, his slave status being a violation of the Missouri Compromise, the Northwest Ordinance, and the Wisconsin Enabling Act.
By 1840 Dred Scott had married another slave of Emerson's, named Harriet, and the couple had a child. Desperate to shake off the yoke of slavery but unable to buy his family's freedom, Scott sued for his freedom in Missouri, arguing that once he had entered free territory he could no longer be a slave.