It is always challenging to know exactly what content to include, how far back to go, and how much time to spend on all of the events building up to the Civil War. Curriculums often include the invention of the Cotton Gin in 1793 and the Missouri Compromise of 1820 as important early developments, but I didn't like teaching them in isolation.
I created this assignment to be a brief but informative link from the creation of the Constitution when our Founding Fathers sanctioned slavery, through the invention of the Cotton Gin which further popularized slavery, to westward expansion which spread slavery, to the Missouri Compromise which officially divided the nation based on slavery. This gives students good context as they dive into the events closer to the war. For those, I suggest my "Civil War: Events Leading to War".