For what reasons did Southern states begin to secede in 1861, and what events led to the breakout of the Civil War?

For what reasons did Southern states begin to secede in 1861, and what events led to the breakout of the Civil War?
You should write a minimum of three paragraphs to earn a passing grade, and each paragraph should be at least 6 sentences long. I need 5 paragraphs.
Why was the Battle of Gettysburg a decisive turning point in the Civil War?
Write a minimum of three paragraphs to earn a passing grade, and each paragraph should consist of a minimum of 6 sentences. The minimum is write 5 paragraphs.