The Dred Scott decision, a landmark ruling by the U.S. Supreme Court in 1857, was pivotal in the context of the pre-Civil War tensions surrounding slavery and citizenship. Dred Scott, an enslaved man who sued for his freedom based on his residence in free territories, ultimately had his case decided against him. The Court ruled that African Americans, whether enslaved or free, could not be considered citizens, thus denying Scott his legal standing. This decision stoked tensions between the North and South, exacerbating the divisions that eventually led to the Civil War.