What was the primary cause of the American Civil War?

The primary cause of the American Civil War was the conflict over slavery. This issue was deeply intertwined with various facets of society and politics in the United States during the 19th century. The southern states' economies were heavily reliant on agriculture, particularly cotton, which depended on slave labor. In contrast, many northern states were moving towards industrialization and were increasingly opposed to the expansion of slavery into new territories and states.

The debate over whether new territories admitted to the Union should be free or slave-holding led to significant tensions and confrontations, including events like the Kansas-Nebraska Act and "Bleeding Kansas." The election of Abraham Lincoln in 1860, a candidate who opposed the spread of slavery, prompted several southern states to secede from the Union, ultimately leading to the outbreak of the Civil War.

While state sovereignty issues, economic differences, and nationalism also played roles in the lead-up to the war, they were largely influenced by and contingent upon the central issue of slavery. The conflict over the institution of slavery fundamentally shaped the political landscape of the era and drove both the secession of southern states and the subsequent military conflict.