Political Causes
One major political cause of the American Civil War was the compromise of 1850. This compromise immediately separated the North and the South because California was admitted as a free-state with popular sovereignty instead of a pro-slavery state. This caused the South to become angry because they wanted a totally pro-slavery state while the North wanted a totally free-state, so neither side was happy with the compromise.
Economic Causes
Ship building, fishing, and lumber were the main industries in the North, and these industries are not slave based at all, while the South was mostly agricultural and farming things like corn, wheat, tobacco, and livestock. These industries were very slave based, which caused a difference in opinion to accumulate and the North's hatred of the South's use of slaves to grow.
Social Causes
A great social cause of the American Civil War was that the North wanted a completely unified nation with one central government while the South wanted separation and state run governments. Also, the Northerners had many more rights and freedoms that the Southerners did not have, which caused envy to grow and hatred to accumulate.
Triggering Event
The triggering event of the American Civil War could be either the compromise of 1850, which caused California to enter as a free state with popular sovereignty which the South did not want at all, or the battle at Fort Sumter, which was considered the first major battle of the Civil War between the North and South. Either of these events could be considered the beginning of the Civil War, but it depends on opinion.