What was one of the key issues that contributed to the outbreak of the Civil War?

One of the key issues that contributed to the outbreak of the Civil War was slavery. The institution of slavery created deep divisions between the Northern and Southern states, where the North was increasingly opposed to the expansion of slavery, whereas the South largely depended on it for their agricultural economy. This fundamental disagreement over human rights and the morality of slavery was a major source of conflict.

The status of slavery in new territories became a particularly contentious issue, leading to events such as the Missouri Compromise and the Kansas-Nebraska Act, which tried to balance the interests of slaveholding and free states. The publication of anti-slavery literature and the abolitionist movement in the North further fueled tensions, while the South's insistence on the continuation and expansion of slavery exacerbated fears of economic and political dominance.

While economic differences, foreign relations, and territorial expansion also played roles in the growing divide between the North and South, it was ultimately the issue of slavery that was at the very heart of the conflict, as it was intertwined with identity, social structures, and state sovereignty. This stark polarization over slavery laid the groundwork for the Civil War, driving both sides to take definitive stands that would lead to armed conflict.