When the War of 1812 ended, the United States consisted of eighteen
states—nine free and nine slave. Very soon Indiana was admitted as a
free state, offset by Mississippi as a slave state. It was inevitable
that this precarious balance between the North and the South would some
day cause trouble, and the trouble came very soon. In 1818, Illinois
entered as a free state, and the enabling legislation to admit Missouri
was introduced in Congress in 1819.
The South assumed that Missouri would be a slave state, but a New York
Congressman amended the Missouri statehood bill to provide for gradual
freeing of the slaves there. The South reacted vigorously to keep from
losing its equal representation in the Senate and blocked passage of the
bill. Meanwhile, Alabama came in to balance Illinois, and there were
eleven northern and eleven southern states.
The following year, when Maine applied for admission into the Union,
Henry Clay of Kentucky engineered the famous Missouri Compromise. This
agreement provided that Missouri would come in as a slave state but that
no more slave states would be admitted from territory north of
Missouri’s southern boundary. This compromise is important because it
foreshadows the struggle between the North and South that eventuated in
the Civil War a generation later. Although most of the oratory dealt
with the slavery issue, the struggle also concerned the broader matter
of political control in the West.