Dred Scott and his master, lived in a slave state (Missouri)
A little while later, Dred Scott and his enslaved family moved to a free state. (Illinois)
Dred Scott's master had died years later, and because of this Scott wanted to become free. He decided to sue his master's widow in order to get enough money to buy his freedom.
Dred Scott first went to State Court, here he was found to still legally be a slave.
Dred Scott then went to Federal Curt, again he was found to be a slave.
Finally, Dred Scott's case was taken up by the Supreme Court. 5 of the justices were Southerners, and seven of them were also Democrats. 7 of the 9 justices were against Scott, because of this Dred Scot was found to still be a slave.