Skeptic Project

According to historian Chandra Manning, both Union and Confederate soldiers who did the actual fighting believed slavery to be the cause of the Civil War. A majority of Confederate soldiers fought to protect slavery, which they viewed as an integral part of southern economy, culture, and manhood. Union soldiers believed the primary reason for the war was to bring emancipation to the slaves. However, many Union soldiers did not fully endorse the idea of shedding their own blood for African American slaves, whom they viewed as inferior. Manning's research involved reading military camp newspapers and personal correspondence between soldiers and families during the Civil War. Manning stated that the primary debate in Confederate states over secession was not over state rights, but rather "the power of the federal government to affect the institution of slavery, specifically limiting it in newly added territories."

http://en.wikipedia.org/wiki/American_Civil_War#Slavery

@muertos as a chicagoan I must say your analogy is off base. That cow was a whore and a damned liar. There is no proof she started the fire! She's a fame slut.

Proctor: All right, here's your last question. What was the cause of the Civil War?
Apu: Actually, there were numerous causes. Aside from the obvious schism between the abolitionists and the anti-abolitionists, there were economic factors, both domestic and inter--
Proctor: Wait, wait... just say slavery.
Apu: Slavery it is, sir.