Did slavery start the Civil War ?
The short answer to this question is no. The Civil War's immediate cause was the Confederate attack on Fort Sumter in April of 1861. A more complex answer would be that the Civil War's causes lay in serious, possibly even irreconcilable political differences between the states of the Deep South and northern states. These differences had their roots in the institution of slavery, and indeed reached their fiercest pitch during debates over whether slavery should be allowed to expand into western territories. They culminated with the secession of the seven Deep South states (South Carolina, Alabama, Mississippi, Texas, Florida, Georgia, and Louisiana) after Abraham Lincoln, whose position was that slavery should not be allowed to expand any further than its present borders, was elected in November of 1860. It was secession which brought the Confederacy and the federal government to the situation they faced at Fort Sumter. Many of the departing states made it quite clear that the defense of slavery was the most important of their reasons for leaving the Union. South Carolina's "Declaration of Causes," issued by the secession convention, is one example:
A geographical line has been drawn across the Union, and all the States north of that line have united in the election of a man to the high office of President of the United States, whose opinions and purposes are hostile to slavery...[H]e has declared that that "Government cannot endure permanently half slave, half free," and that the public mind must rest in the belief that slavery is in the course of ultimate extinction.
The Declaration, which was fairly typical of those issued by the secession conventions, went on to decry the fact that in some northern states, black men were allowed to vote. So while slavery did not start the Civil War, the issue of slavery was foremost among the causes for secession among the states who first left the Union.
I guess President Lincoln met the writer in 1862 !
The "cause" of the war was the attack, the cause of the attack was the secession of the southern states, the cause of the secession was the future of slavery, and the cause of the question of the future of slavary was SLAVERY itself.
So we can say that the cause of the war WAS SLAVERY.
When President Lincoln first met Harriet Beecher Stowe in 1962, the author of Uncle Tom's Cabin, he remarked "So you're the little woman who wrote the book that started this great war." This may be a legend, though in any case it does reveal much about the possible connection between the widespread popularity of the novel and the boiling antagonism between the North states and the south in the 1850's.