The Dred Scott Supreme Court decision in 1857 was significant because it declared that African Americans, whether enslaved or free, could not be American citizens and thus had no legal standing to sue in federal court. This ruling intensified national divisions over slavery, particularly undermining the Missouri Compromise by asserting that Congress could not regulate slavery in the territories. The Court's decision fueled abolitionist sentiment in the North and further entrenched the institution of slavery in the South. It also set the stage for heightened tension leading up to the Civil War, exemplifying the deep-seated racial and legal inequalities of the time.