Which issue was a major problem leading to the Civil War?

The major issue leading to the Civil War was slavery. This institution created deep social, political, and economic divisions between the North and South. In the South, the economy heavily relied on slave labor for agricultural production, particularly in the cotton industry, which was a cornerstone of their economic prosperity. Conversely, the Northern states had largely moved towards a more industrialized economy that did not depend on slavery and began opposing its expansion into new territories.

As tensions grew over whether new states and territories admitted to the Union would be free or slave states, this conflict intensified, leading to significant political battles such as the Missouri Compromise and the Compromise of 1850. The election of Abraham Lincoln in 1860, who was seen as anti-slavery, further exacerbated these tensions, culminating in the Southern states' secession. The issue of slavery was at the heart of the moral and ethical debates of the time and directly affected national policies and conflicts, making it the primary catalyst for the Civil War.

While women's rights, economic growth, and expansionism were significant issues in American history, they did not play as central a role in the immediate causes of the Civil War as slavery did, which fundamentally shaped the national conversation at that time.