At that time, counting the States as they were finally classified, eight were destined to be slave and eight free.

Ohio entered the Union as a State in 1802, thus giving to the free States a majority of one.

The balance, however, was restored in 1812 by the admission of Louisiana as a slave State.

The admission of Indiana in 1816 on the one side and of Mississippi in 1817 on the other still maintained the balance: ten free States stood against ten slave States.
During the next two years Illinois and Alabama were admitted, making twenty-two States in all, still evenly divided.
The ordinance for the government of the territory north of the Ohio River, passed in 1787 and reenacted by Congress after the adoption of the Constitution, proved to be an act of great significance in its relation to the limitation of slavery.

By this ordinance slavery was forever prohibited in the Northwest Territory.