State rights
It was the struggle between the government and individual states about political power. This was focused on if the federal government was able to abolish slavery upon each state. The First US government after the American Revolution was the Article of Confederation. The 13 states made a very small weak government. When a problem arose, the tiny group of leaders secretly made The US Constitution. Jefferson was not at this meeting because he thought that each state should have the freedom to choose if they want this kind of government. Thus the idea of nullification was thought up of. It is the idea that states would have the right to rule federal acts unconstitutional. Unfortunately, the federal government denied this request of freedom. When they thought about it, they led to secession which is to leave+. This caused disharmony between the North and South states and slowly began the Civil War.
Slavery
The debate was about the future of slavery and what would happen with or without slavery. This bought secession between the North and South, the North wanted to preserve the Union, and the South wanted to establish Southern independence in their confederation. There were many compromises between states that did or didn't believe in slavery. Then, there was the fugitive slave act which are laws for runaway slaves. The northerners did not agree with this law but when they saw a slave they HAD to turn them in because of the law. The South wanted slaves because of agriculture and cotton because if there weren't enough people to do this task, it would be hard to survive. The North on the other hand, has more city life rather than the South and there were factories and gods were made there instead of farming. The North didn't need the slaves because they already had machines to do it for them.
Westward Expansion
This might have stated the Civil War because they have debated over if some territories could be considered states because of their views of slavery, and if slavery was legitimate, etc..... The debates over this issue were discussed in the early or mid- 1800s. The most thought reason that this brought the Civil War is when the expanded the West, there was more debate over if slavery should be allowed or not.
Citations
http://americanhistory.about.com/od/civilwarmenu/a/cause_civil_war.htm
http://www.harlingen.isd.tenet.edu/coakhist/cwar.html
http://www.harlingen.isd.tenet.edu/coakhist/cwar.html