What was one of the issues that led to the Civil War?

Slavery was a central issue that led to the Civil War in the United States. The conflict primarily arose from the deep-seated differences between the Northern states, which were largely anti-slavery and sought to prevent its expansion, and the Southern states, which relied heavily on an agrarian economy supported by slave labor. The moral and ethical debates over slavery, along with legislative attempts to balance power between free and slave states, created significant tensions. This included events such as the Missouri Compromise, the Dred Scott Decision, and the rise of abolitionist movements. Ultimately, these unresolved issues ignited a full-scale war when Southern states seceded from the Union after the election of Abraham Lincoln, who was perceived as a threat to the institution of slavery.

While trade tariffs, immigration, and foreign policy were relevant topics during that period, they did not carry the same weight or direct impact on the decision to go to war as slavery did. The question specifically highlights a fundamental disagreement over the morality and legality of slavery, which was a driving force behind the Civil War.