What was one issue that led to the split in the American slavery society?

One significant issue that led to the split in American society over slavery was the debate over the expansion of slavery into new territories and states. As the United States expanded westward, conflicts arose between pro-slavery and anti-slavery factions, particularly over whether new states admitted to the Union would be free or slave states. This tension was exemplified by events such as the Missouri Compromise and the Kansas-Nebraska Act, which only intensified sectional divisions and ultimately contributed to the outbreak of the Civil War.