1. Economic and social differences between the North and the South.
2. States versus federal rights.
3. The fight between Slave and Non-Slave State Proponents.
4. Growth of the Abolition Movement.
5. The election of Abraham Lincoln. - What were the main reasons for the start of the civil war? - Yahoo! Answers
Hmmm... looks like your revisionist history class has failed you yet again.
Top Five Causes of the Civil War
You mite also want to get the Southern view...
Causes of the Civil War (Confederate View)