Final answer:
The Dred Scott v. Sandford decision ruled that a slave could not obtain freedom through residing in a free state or territory. The court also declared that black people could not be U.S. citizens.
Step-by-step explanation:
The Supreme Court's Dred Scott v. Sandford decision ruled a slave, specifically Dred Scott, could not gain freedom by being taken to a free state or territory. This controversial ruling declared that the relevant parts of the Missouri Compromise, which had designated certain states as free of slavery, were unconstitutional. Even though Scott had been brought into free territories by his owner, he was considered to remain a slave upon returning to a slave state. Furthermore, the court declared that black people, whether they were free or enslaved, were not and could never be citizens of the United States.
Learn more about Dred Scott v. Sandford