One of the major causes of the civil war had to do with the expansion of the United States and the conflict over whether new states would be admitted to the Union as slave states or free states. Though the Missouri Compromise was considered to be a partial solution, many people felt that it set in motion an unstoppable slide towards the war.
Nat Turner's slave rebellion in 1831 also caused Virginian lawmakers to remove some basic civil rights that had been accorded to slaves contributing to further unrest.
The Compromise of 1850, intended as a further band-aid to problems inherent in the westward expansion of the United States also pushed the country closer to open conflict.
John Brown's raid in 1859 coupled with the election of Abraham Lincoln and his Republican Party's anti-slavery position led to the secession of South Carolina which was then followed by other southern states in 1860.
An attempt to re-supply Fort Sumter triggered a Southern response, the first open battle of the Civil War that would lead to the surrender of Fort Sumter and the onset of the Civil War.
The Civil war started over differences in the economies in the North and South. While the Northern states had begun to industrialize, the south relied on agriculture. Mainly the production of cotton and tobacco. The south's economy was threatened by the abolition of slavery, because having to pay workers would cripple their profits. When Abraham Lincoln was elected president the South feared that slavery would be ended and succeeded from the Union.
Other events that led to beginning of the civil war include: Bloody Kansas Massacre, Kansas/Nebraska Act, The Dred Scott decision, and the 3/5 compromise.