Dred Scott was an African American (then "Negro") slave who was owned by Dr. Emerson, a surgeon in the United States Army. In the course of his travels, Emerson took Scott from his home state of Missouri to military posts in Illinois and other parts of the former Louisiana Territory. At that time, Missouri was part of the former Louisiana Territory, which had been ceded to the United States by France under the terms of the Louisiana Purchase. In 1821, Missouri was separated out from the territory as its own state under the Missouri Compromise of 1820, which maintained that slavery was thereby forbidden in all of the former Missouri Territory except for the newly-formed state of Missouri. Thus, in his travels, Emerson had taken Scott to states in which slavery was forbidden. After his return to Missouri, Scott sued Emerson claiming that his travels in the free states had made him a free man. Eventually, the United States Supreme Court ruled that Scott could not sue for his freedom because he could never be a U.S. citizen who would have access to the U.S. courts to bring such a lawsuit.
Scott sued first in Missouri state court, relying on significant judicial precedent for his argument (Scott v. Emerson, 15 Mo. 576 (1852)). Prior to the Court's decision in Scott, there had been a long list of Missouri cases that held that a master lost property rights in his slaves when he took them into free territories. The most notable of these cases was the Missouri Supreme Court's decision in Winny v. Phoebie Whitesides, 1 Mo. 473 (1824), in which the court held that a slave had become free because she had resided in the free territory of Illinois in 1799. Specifically, the court stated that the U.S. Constitution's interstate comity provision required that Winny's status as a free person in Illinois made her a free person in Missouri under the terms of the Northwest Ordinance (1787, which banned slavery north and west of the Ohio River)....