To balance the number of "slave states" and "free states," the northern region of what occurred as a result of a compromise involving slavery in Missouri, and in the federal territories of the American west.
To balance the number of "slave states" and "free states," the northern region of what was then Massachusetts ultimately gained admission into the United States as a free state to become Maine. This only occurred as a result of a compromise involving slavery in Missouri, and in the federal territories of the American west.