At the beginning 19. Century was split the American nation in the question of the slave attitude. The USA consisted of 11 slave owner states in the south and 11 slave-free states in the north. When the Missouri territory should be taken up as the further state to the USA, this equilibrium was endangered.
The smoldering controversy became to 20. March after a collecting main settled by Henry Clay: The Maine separated from Massachusetts was taken up 1820 as slave-free State of member of the union and the Missouri 1821 as slavery approving of state to the USA, with which in the senate the parity between the north and the south remained. The Nebenbestimmung that in the Louis IANA - territory north of 36°30 `the slavery to be forbidden is, 1854 with the Kansas Nebraska act was waived.