What was the main cause of the American Civil War?

The main cause of the American Civil War was indeed slavery and states' rights. This conflict arose primarily from the deep-seated divisions between the Northern states, which favored a more centralized federal government and the abolition of slavery, and the Southern states, which championed states' rights and sought to preserve the institution of slavery.

The debate over whether new territories admitted to the Union should be free or slave states intensified these tensions. Southern states believed they had the right to determine their own laws regarding slavery without federal interference, leading to arguments for states' rights. Ultimately, the election of Abraham Lincoln, who opposed the expansion of slavery, was seen by Southern states as a threat to their way of life and led them to secede from the Union, triggering the Civil War.

This choice encapsulates the economic, social, and political factors that fundamentally divided the nation, leading to a conflict that would alter the course of American history.