What were the causes of the American Civil War?

The full restoration of the Union was the work of a highly contentious postwar era known as Reconstruction. The war produced about 970,000 casualties (3% of the population), including approximately 620,000 soldier deaths - two-thirds by disease. The causes of the war, the reasons for its outcome, and even the name of the war itself are subjects of lingering controversy even today. The main results of the war were the restoration and strengthening of the Union, and the end of slavery in the United States.