What is the Missouri Compromise and its significance?

Due to the growing conflict between slave states and free
states in the early nineteenth century, the Missouri Compromise was drafted as a way to
create agreement between the two sides prohibiting slavery in new territories in the
former Louisiana territory except for the newly formed state of Missouri which would be
a slave territory.  Any area above the parallel of 36 30 north would be designated as
free territory.

During its passage through congress the
measure also acquired the admittance of Maine and Alabama as free and slave states
respectively, thus equaling the number of slave and free states in the
Union.

Jefferson, among others, felt that this division
would eventually lead to a divided nation and the act was eventually repealed by the
Kansas-Nebraska Act in 1854.