It was a mere accident that the line drawn by Mason and Dixon
between Pennsylvania and Maryland became known in later years as
the dividing line between slavery and freedom. The six States
south of that line ultimately neglected or refused to abolish
slavery, while the seven Northern States became free. Vermont
became a State in 1791 and Kentucky in 1792. The third State to
be added to the original thirteen was Tennessee in 1796. 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. In the territory south of the Ohio River slavery
became permanently established. The river, therefore, became an
extension of the original Mason and Dixon's Line with the new
meaning attached: it became a division between free and slave
territory.

It was apparently at first a mere matter of chance that a balance