Missouri Compromise

The 1820 U.S. law admitted Missouri as a slave state and Maine as a free state, while prohibiting slavery in much of the Louisiana Purchase north of latitude 36°30′.

Maine: A U.S. state in New England, admitted to the Union in 1820 as a free state. Its admission as a free state balanced Missouri’s entry as a slave state.
Tallmadge Amendment: A 1819 proposal to restrict slavery in Missouri and gradually emancipate enslaved people born there. Its rejection sharpened the conflict that produced the compromise.
Compromise of 1850: A package of U.S. laws addressing slavery and territorial status after the Mexican–American War. It replaced the Missouri line with a different political settlement for new territories.
Popular sovereignty: The principle that residents of a territory should decide whether to permit slavery. Unlike the compromise’s fixed latitude boundary, this approach left the decision to settlers.
Missouri: A U.S. state in the central United States, admitted to the Union in 1821 as a slave state. Its admission triggered the dispute that the law resolved.
Missouri statehood crisis: The 1819–1821 congressional conflict over Missouri’s admission and the expansion of slavery. This crisis directly prompted the compromise’s enactment.
Kansas–Nebraska Act: The 1854 law organizing Kansas and Nebraska territories and allowing settlers to decide slavery by popular sovereignty. It repealed the Missouri Compromise’s restriction north of 36°30′.
Wilmot Proviso: An 1846 proposal to prohibit slavery in territory acquired from Mexico, which never became law. It sought a territorial slavery ban but failed, unlike the enacted Missouri restriction.
36°30′ parallel: The line of latitude 36°30′ north, used in the Missouri Compromise to delimit slavery restrictions in the Louisiana Purchase. The law prohibited slavery north of this line, except in Missouri.
Sectionalism in the United States: Political division in the United States organized around regional interests and identities. North–South sectional divisions made Missouri’s status a national power struggle.

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