Dred Scott was a black slave who was owned by John Emerson, who had bought him and his wife from Peter Blow of St. Louis. When John Emerson died, the Blows helped Dred Scott and his wife sue for freedom. However, they lost the case in State court.
Dred Scott then sued again, claiming that since his new owner, John Stanford, was a New York citizen, and he was a Missouri citizen, he should be set free. Scott's lawyers appealed the case until it reached the U.S. Supreme Court.
The members of the Supreme Court who were northerners ruled that Scott was free because he had traveled north of the 36-30' Mason-Dixon line. However, Southern members of the Supreme Court interpreted the Missouri Compromise as unconstitutional. In 1857, Chief Justice Roger B. Taney ruled that blacks could not become citizens whether they were slaves or freedmen. The Dred Scott decision was an important Supreme Court decision which magnified the state of racial injustice before the Civil War.