The event characterized by the debate over states' rights in the U.S. is the American Civil War (1861–1865). Central to the conflict was the tension between federal authority and states' rights, particularly regarding issues like slavery and taxation. Southern states advocated for their right to govern themselves and maintain slavery, while the Northern states pushed for a stronger federal government to unify the nation and abolish slavery. This debate on states' rights not only led to the war but also shaped future discussions on federalism and civil liberties in American politics.