(1820) Act passed by the U.S. Congress admitting Missouri to the Union as the 24th state. After the territory requested statehood without slavery restrictions, Northern congressmen tried unsuccessfully to attach amendments restricting further slaveholding. When Maine (originally part of Massachusetts) requested statehood, a compromise led by Henry Clay allowed Missouri admission as a slave state and Maine as a free state, with slavery prohibited from then on in territories north of Missouri's southern border. Clay's compromise appeared to settle the slavery-extension issue but highlighted the sectional division.
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Series of compromises in 1860–61 intended to forestall the American Civil War. Sen. John J. Crittenden proposed constitutional amendments that would reenact provisions of the Missouri Compromise and extend them to the western territories, indemnify owners of fugitive slaves whose return was prevented by antislavery elements in the North, allow a form of popular sovereignty in the territories, and protect slavery in the District of Columbia. The plan was rejected by president-elect Abraham Lincoln and narrowly defeated in the Senate.
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Series of measures passed by the U.S. Congress to settle slavery issues and avert secession. The crisis arose in late 1849 when the territory of California asked to be admitted to the Union with a constitution prohibiting slavery. The problem was complicated by the unresolved question of slavery's extension into other areas ceded by Mexico in 1848. In an attempt to satisfy pro- and antislavery forces, Sen. Henry Clay offered a series of measures that admitted California as a free state, left the question of slavery in the new territories to be settled by the local residents, and provided for the enforced return of runaway slaves and the prohibition of the slave trade in the District of Columbia. Support from Daniel Webster and Stephen A. Douglas helped ensure passage of the compromise. Moderates throughout the Union accepted the terms, which averted secession for another decade but sowed seeds of discord.
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Research has indicated that suboptimal compromises are often the result of fallacies such as the fixed sum error and the incompatibility error, leading to the misperception that the other side's interests are directly opposed. Mutually better outcomes can be found by careful investigation of both parties' interests.