Answer + Explanation:
The Supreme Court decision that divided the nation over the issue of slavery was Dred Scott v. Sandford, which was handed down on March 6, 1857. In this case, the Supreme Court ruled that African Americans, whether free or enslaved, could not be considered citizens of the United States and therefore could not sue for their freedom in federal court. The Court also declared that the Missouri Compromise, which had prohibited slavery in certain territories, was unconstitutional, effectively opening up all territories to slavery. This decision was seen as a major victory for the pro-slavery forces in the United States and further inflamed tensions between North and South in the years leading up to the Civil War.