The Dred Scott case was a significant event that contributed to tensions before the Civil War. Dred Scott was a slave who sued for his freedom, claiming that he had been taken by his owner to live in free territories and therefore should be considered a free man. The case eventually made its way to the Supreme Court, which ruled in 1857 that Scott was not a citizen and did not have the right to bring a lawsuit.
This ruling was seen as a major victory for slaveholders and a defeat for abolitionists, as it effectively declared that no black person, whether free or slave, could be a citizen of the United States. The Dred Scott decision was widely criticized and further inflamed tensions between the North and South, as it was seen as a clear example of the Southern states' desire to protect and expand slavery. The ruling was also one of the factors that led to the outbreak of the Civil War in 1861.