I agree with bozewani, slavery was the root cause of the Civil War, but it also involved economic and social issues.
Southern plantation owner believed without slavery there would not a free labor force; Many immigrants passed through southern as well as northern ports. Slavery stifled economic growth of the south, as many people who came south to start a business left discouraged as slavery left no market for their goods and services.
Northerners felt that slavery held down wages and prevented the United States to compete equally with foreign good.
Socially, the North and South were far apart. Southern society mirrored the priveleged aristocracy, and smacked of despotism.
Northerners were influneced by the flood of European immigrants, many fleeing wars, revolutions and famine. They believed in popular democracy, the right of the majority to set the norms the economic and social norms.
The Civil War pitted aristocratic, priveleged planters against those the believed that the abolition of slavery would allow the nation to progress in industry, commerce and expansion.