A controversial ruling made by the Supreme Court in 1857, shortly before the outbreak of the Civil War. Dred Scott, a slave, sought to be declared a free man on the basis that he had lived for a time in a “free” territory with his master. The Court decided that, under the Constitution, Scott was his master's property and was not a citizen of the United States. The Court also declared that the Missouri Compromise, which prohibited slavery in certain areas, unconstitutionally deprived people of property — their slaves. The Dred Scott decision was a serious blow to abolitionists (see abolitionism).