The Missouri Compromise Draws a Line Through Slavery
One free state, one slave state, and a line across the map to keep the balance
Quick facts
- Passed
- March 1820
- Balance struck
- Missouri (slave) and Maine (free) admitted together
- The line
- Slavery barred north of 36 degrees 30 minutes latitude
- Status
- A temporary settlement of a recurring crisis
What happened
As settlers pushed west into the land bought in the Louisiana Purchase, the question of whether new states would allow slavery threatened to break the union apart. Missouri applied to join as a slave state in 1819, which would have tipped the even balance of free and slave states in the Senate. Congress found a temporary answer in the Missouri Compromise, passed in March 1820: Missouri entered as a slave state and Maine as a free state at the same time, keeping the balance, and slavery was prohibited in the rest of the Louisiana Territory north of the line of 36 degrees 30 minutes latitude. It settled the immediate crisis but drew a literal line dividing the country into competing halves, half free and half slave.
Why it matters
The Missouri Compromise revealed that slavery was the fault line running through American expansion, and that each new state would reopen the wound. The 36 degrees 30 minutes line held for a generation before the Kansas-Nebraska Act and the Dred Scott decision tore it up, and the failure of these compromises to hold pushed the country toward civil war.
How we know
The compromise legislation and its 36 degrees 30 minutes provision survive in the statutes passed by Congress in 1820, preserved in the National Archives and the records of the U.S. Senate.
Sources
- National Archives. Missouri Compromise (1820) · Primary source (author-declared)archives.gov · Cited as a "primary" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
- United States Senate, Senate Historical Office. The Missouri Compromise · Reputable sourcesenate.gov · The domain "senate.gov" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
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