Krispy is right. Slavery was not the exclusive reason for the war but I would like to add, that although slavery was not the singular cause of the Civil War it was at the heart of the sectional impasse between North and South in 1860 and had been a problem for many years before.
Republicans opposed the expansion of slavery into territories owned by the United States, and their victory in the presidential election of 1860 resulted in seven Southern states declaring their secession from the Union even before Lincoln took office. The Union rejected secession, regarding it as rebellion.
Confederate Vice President Alexander Stephens said that slavery was "the cornerstone of the Confederacy" after Southern states seceded. After Southern defeat, Stephens said that the war was not about slavery but states' rights, and became one of the most ardent defenders of the Lost Cause. Confederate President Jefferson Davis also switched from saying the war was caused by slavery to saying that states' rights was the cause.
All but one inter-regional crisis involved slavery, starting with debates on the three-fifths clause and a twenty year extension of the African Slave Trade in the Constitutional Convention of 1787. There was controversy over adding the slave state of Missouri to the Union that led to the Missouri Compromise of 1820, the Nullification Crisis over the Tariff of 1828 (although the tariff was low after 1846), the Gag rule that prevented discussion in Congress of petitions for ending slavery from 1835–1844, the acquisition of Texas as a slave state in 1845 and Manifest Destiny as an argument for gaining new territories where slavery would become an issue after the Mexican-American War (1846–1848), which resulted in the Compromise of 1850.
Source [url=http://en.wikipedia.org/wiki/American_Civil_War]here[/url]
Sorry for getting off subject. Go OK!