The Missouri compromise wanted to extend slavery into other states. Congress accepted Missouri as a slave state and also admitted Maine as a free state. By 1819, the United States was formed by twenty two states that were evenly divided between slave and free. The admission of Missouri as a slave state would upset the balance. And when it was being organized as a territory, representatives of New York proposed a law that would have ended slavery there but it was denied, similar as happened in the Arkansas territory.