The Dred Scott Decision (1857) This historic decision stated that even if a slave has resided or resides in a state where slavery was prohibited, he would not be considered free. Moreover, the ruling stated that the African Americans would not be considered as the US citizens. It also declared the Missouri Compromise (1820) as unconstitutional. These rulings exacerbated the then existing sectional controversy while, at the same time, pushing the United States to the brink of a civil war.