6. The Civil War (1861-1865)
The Civil War stands as the most dramatic moment when the United States nearly ceased to exist as a single nation. Eleven Southern states seceded, forming the Confederate States of America in open defiance of federal authority. For four years, Americans fought the deadliest war in the nation’s history, with families and communities torn apart by their loyalties. In the end, the Union endured—but at an immense cost, both in lives and national trauma. The Civil War’s legacy still shapes American society today. Learn more
