The issue of slavery was the primary cause of the American Civil War. The institution of slavery was deeply ingrained in the Southern economy and society and had become a contentious topic in American politics. The Northern states were largely against the practice, while the Southern states were staunchly in favor of preserving it. Attempts to compromise on the issue, such as the Missouri Compromise and the Compromise of 1850, failed to prevent a growing rift between the two regions. The election of Abraham Lincoln, who opposed the spread of slavery, in 1860 was seen as a threat by Southern slave states, and eleven of them ultimately seceded from the Union, leading to the outbreak of war.