In 1834, Dred Scott, a slave, had been taken to Illinois, a free state, and then Wisconsin territory, where the Missouri Compromise of 1820 prohibited slavery. ... In 1846, after Emerson died, Scott sued his master's widow for his freedom on the grounds that he had lived as a resident of a free state and territory.
He sued because the state his owner moved him to it was illigal to own slaves so he sued the owner. And Dred Scott won and got freedom for him and wife and his 2 kids.
