Under the Missouri Compromise of 1820, Maine is added as a free state. Previously, the land had been part of Massachusetts. This satisfies those who opposed the expansion of slavery as well as "slave powers" in Congress.
No more slaves !!!
A major provision of the Missouri Compromise was that slavery was not to exist above 36* 30' N. This satisfied the North, since slavery would not be able to expand past this imaginary line drawn across the Louisiana Purchase.
For the Northern free states , New York Senator James Tallmadge proposed an amendment banning slavery in the Louisiana territory. In addition, Senator Rufus King also argued Congress had the power to determine whether or not a new state could have slavery.
No more slaves past Louisiana.
You have the power to decide whether new states can have slaves or not.
For the Southern slave holding states, Missouri is added to the Union as a slave state. Although it exist above dividing line, the addition of Missouri as a slave state provides balance to the Union in terms of free and slave states, and representation in Congress.
To satisfy the South, it was agreed that that slavery was agreed that slavery could expand and exist below the dividing line drawn across the Louisiana Purchase. This ensured some expansion of slavery for the South, including future states such as Texas and Arkansas .
Fine, slaves can be slaves under the DIviding draw line only.
For the southern slave advocates, Maryland Senator William Pickney held the belief states should be able to decide the nature of whether or not they are slave or free. Ultimately, Senator Henry Clay will devise the Missouri Compromise, ending the debate.