States Rights and Slavery
I have written about this issue as well. Most detailed analysis I have done is here.
To me the Civil War was probably inevitable given how our nation was founded. I believe in order to move on from the shame of slavery and the trauma of the Civil War, we have to face up to the real issues of the Civil War, not sugar coat it for the benefit of the side that lost. America was FOUNDED with slavery as part of its very system. That is to all our shame. The South was the last part to defend the institution of slavery. That is the shame of the South. We, as a nation, have NEVER faced up to the shame and impact of slavery. That is to all our shame. So let's be honest about it so we can really deal with its long term consequences.