Northern Concerns Over Missouri's Admission as a Slave State

Missouri's 1820 bid for statehood as a slave state threatened the Senate's delicate balance—11 free vs. 11 slave states. Northern states feared:

• Upsetting sectional equilibrium.
• Setting a precedent for slavery's expansion into Louisiana Purchase territories.
• Permanent entrenchment of slavery westward.

The Missouri Compromise (1820) temporarily resolved the crisis by admitting Missouri as slave, Maine as free, and banning slavery north of 36°30′.