Final answer:
In the historic Dred Scott v. Sanford case, the Supreme Court ruled that Dred Scott was not a U.S. citizen and could not sue for freedom, confirmed the status of slaves as property, and declared that Congress could not ban slavery in the territories.
Step-by-step explanation:
In the Dred Scott v. Sanford decision, the U.S. Supreme Court made several key rulings. Firstly, it declared that Dred Scott was not a U.S. citizen due to his status as an African American descended from slaves. Consequently, Scott had no standing to sue in federal court. Secondly, the Court ruled that slaves are considered property, and therefore, the residence of a slave in a free territory did not grant freedom upon returning to a slave state. The ruling also stated that Congress lacked the authority to prohibit slavery in the territories, effectively declaring the Missouri Compromise unconstitutional.