The American Civil War was the most deadly and arguably the most important event in the nation's history. Sectional tensions erupted in the constitution causing a brutal war that cost over 600,000 lives and seperated a nation in two.
Slavery was a cause of the conflict, and while the thirteenth amendment ended the practice at war's end, race relations continued to dominate American politics and society well into the future. The war also increased American economic power until it rivaled, and then surpassed, that of all other countries.