Why did the Missouri compromise of 1820 and 1850 fall apart?

In 1820, amid growing sectional tensions over the issue of slavery, the U.S. Congress passed a law that admitted Missouri to the Union as a slave state and Maine as a free state, while banning slavery from the remaining Louisiana Purchase lands located north of the 36º 30’ parallel.

The Missouri Compromise, as it was known, would remain in force for just over 30 years before it was repealed by the Kansas-Nebraska Act of 1854. In 1857, the Supreme Court ruled the compromise unconstitutional in the Dred Scott case, setting the stage for the nation’s final path toward the Civil War.

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