What would have happened in 1818 if missouri had joined the union as a slave state?

The Missouri Compromise was a United States federal statute devised by Henry Clay. It regulated slavery in the country's western territories by prohibiting the practice in the former Louisiana Territorynorth of the parallel 36°30′ north, except within the boundaries of the proposed state of Missouri. The compromise was agreed to by both thepro-slavery and anti-slavery factions in the United States Congress and passed as a law in 1820, under the presidency of James Monroe. 

Had Missouri became a slave state, it could have sparked more tensions between the North and South leading to the American Civil War.