Dred Scott in Causes of the Civil War
Dred Scott (1795-1858) was a slave who, in the 1840s, chose to sue his master's widow for his freedom. He argued that his master, John Emerson, escorted him onto free soil in Illinois and the Wisconsin Territory, so he'd legally—even if inadvertently—granted him freedom.
In 1857, the case reached the United States Supreme Court. The justices ruled against Scott. John Emerson's widow had since remarried, and she returned Scott, his wife, and his daughters to their owners, the Blow family, in May 1857, just months after the ruling.
Both Dred and Harriet Scott died shortly thereafter, never to witness the legacy of their fight. The Dred Scott case was a major event on the road to the Civil War.
The Supreme Court's ruling was a provocative opinion. It stated flatly that Blacks had "no rights which the white man was bound to respect" and rejected the right of any territory to ban slavery within its own borders. Inflaming public opinion in the North, the case led to a hardening of antislavery attitudes and a surge in popularity for the new antislavery Republican Party.