In the mid-19th century, a controversial Supreme Court case intensified the national debate over slavery and citizenship. In this case, an enslaved African American man, Dred Scott, sued for his freedom based on his having been taken temporarily to a free state. Learn how the Supreme Court ruled that African Americans, whether enslaved or free, could never be American citizens and had no standing to sue in federal court. Understand how Chief Justice Roger B. Taney's opinion declared the Missouri Compromise unconstitutional, exacerbating sectional tensions, and contributing to the outbreak of the Civil War and the eventual abolition of slavery.