<human>:  What were the main causes of the American Civil War?
<bot>: The main causes of the American Civil War were primarily rooted in disputes over the institution of slavery, states' rights, and sectional differences that had been simmering for decades prior to the 1860 election of Abraham Lincoln. Slavery was a key factor in the war, as the South's economy was heavily dependent on the institution and the northern states wished to abolish it. Another major cause of the war was the disagreement over states' rights - whether states had the authority to nullify federal laws and the secession of some southern states from the Union. Lastly, different sections of the country had different economies and cultures, often pitting the North and South against each other.