What was the main cause of the American Civil War?

The main cause of the American Civil War was deeply rooted in the question of slavery and states' rights. As the nation expanded westward, the debate intensified over whether new states admitted to the Union would permit slavery. This conflict created significant tensions between the Northern states, which were generally anti-slavery, and the Southern states, which sought to preserve and expand the institution of slavery.

The idea of states' rights also played a crucial role, as Southern states argued they had the authority to decide for themselves whether to allow slavery. This belief was central to their arguments for secession from the Union when they felt their way of life and economic interests—heavily dependent on slavery—were threatened by Northern policies and attitudes.

While trade tariffs, foreign policy disagreements, and expansion issues were factors leading to regional tensions, they were not the primary catalyst for the conflict. The slavery question, intertwined with the Southern states' desire for autonomy, was the most significant underlying cause of the war.