The Missouri Compromise

How Views on Enslavement Transformed the Map of the United States

United States, 1821
Map showing the anti-slavery states, states undergoing gradual abolition, free states via the Ordinance of 1787, free states via the Missouri Compromise, and pro-slavery states in 1821.


Interim Archives /Getty Images 

The Missouri Compromise was the first of the major 19th-century attempts by Congress intended to ease regional tensions over the issue of enslavement. While the deal hammered out on Capitol Hill accomplished its immediate goal, it only served to postpone the eventual crisis that would ultimately divide the nation and lead to the Civil War.

A Nation Sundered by Enslavement

In the early 1800s, the most divisive issue in the United States was enslavement. Following the American Revolution, most states north of Maryland began programs of gradually outlawing the practice, and by the early decades of the 1800s, pro-slavery states were primarily in the South. In the North, attitudes against enslavement were growing increasingly strong, and as time passed the passions over the issue threatened repeatedly to shatter the Union.

The Missouri Compromise of 1820 attempted to resolve the question of whether or not enslavement would be permitted in new territories being admitted as states to the Union. As part of the agreement, Maine would be admitted as an anti-slavery state and Missouri as a pro-slavery state, thereby preserving the balance. With the exception of Missouri, the act also banned enslavement in areas north of the 36° 30′ parallel. The legislation was the result of a complex and fiery debate, however, once enacted, it did seem to reduce tensions—for a time.

The passage of the Missouri Compromise was significant as it was the first attempt to find some resolution to the issue of enslavement. Unfortunately, it did not solve the underlying problems. After the act went into effect, pro-slavery states and anti-slavery states with their firmly ingrained beliefs remained, and the divisions over enslavement would take decades, along with a bloody Civil War, to resolve.

The Missouri Crisis

The events leading up to the Missouri Compromise began with Missouri's application for statehood in 1817. After Louisiana itself, Missouri was the first territory within the area designated by the Louisiana Purchase to apply for statehood. The leaders of the Missouri territory intended the state to have no restrictions on enslavement, which aroused the ire of politicians in northern states.

The “Missouri question” was a monumental issue for the young nation. When asked for his views on it, former president Thomas Jefferson wrote:

"This momentous question, like a fire bell in the night, awakened and filled me with terror."

Controversy and Compromise

New York Congressman James Talmadge sought to amend the Missouri statehood bill by adding a provision stating that no more enslaved people could be brought into Missouri. Talmadge’s amendment also proposed that the children of enslaved people already in Missouri (which were estimated at about 20,000) be set free at the age of 25.

The amendment provoked enormous controversy. The House of Representatives approved it, voting along sectional lines. However, the Senate rejected it and voted there would be no restrictions on enslavement in the State of Missouri.

Meanwhile, Maine, which was set up to be a free state, was being blocked from joining the Union by Southern senators. The matter was eventually worked out in the next Congress, which convened in late 1819. The Missouri Compromise dictated that Maine would enter the Union as a free state, and Missouri would enter as a pro-slavery state.

Henry Clay of Kentucky was Speaker of the House during the Missouri Compromise debates and was deeply engaged in moving the legislation forward. Years later, he would be known as "The Great Compromiser," in part because of his work on the landmark deal.

The Impact of the Missouri Compromise

Perhaps the most important aspect of the Missouri Compromise was the agreement that no territory north of Missouri’s southern border (the 36° 30' parallel) would be allowed to enter the Union as a pro-slavery state. That part of the agreement effectively stopped enslavement from spreading to the remainder of the area included in the Louisiana Purchase.

The Missouri Compromise, as the first great federal agreement over the enslavement issue, was also important in setting the precedent that Congress could regulate enslavement in new territories and states. The question as to whether the federal government had the authority to regulate enslavement would be hotly debated decades later, especially during the 1850s.

The Kansas-Nebraska Act

The Missouri Compromise was ultimately repealed in 1854 by the Kansas-Nebraska Act, which effectively eliminated the provision that enslavement would not extend north of the 30th parallel. The legislation created the territories of Kansas and Nebraska and allowed the population of each territory to determine whether or not enslavement would be permitted. This led to a series of confrontations that became known as Bleeding Kansas, or the Border War. Among the anti-enslavement fighters was abolitionist John Brown, who would later become famous for his raid on Harpers Ferry.

The Dred Scott Decision and the Missouri Compromise

Controversy over enslavement continued into the 1850s. In 1857, the Supreme Court ruled on a landmark case, Dred Scott v. Sandford, in which enslaved African American Dred Scott sued for his freedom on the grounds that he had lived in Illinois, where enslavement was illegal. The court ruled against Scott, declaring that any African American, enslaved or free, whose ancestors had been sold as enslaved people could not be an American citizen. Since the court ruled that Scott was not a citizen, he had no legal grounds to sue. As part of its decision, the Supreme Court also declared that the federal government had no authority to regulate enslavement in the federal territories, and ultimately, led to the finding that the Missouri Compromise was unconstitutional.

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McNamara, Robert. "The Missouri Compromise." ThoughtCo, Jul. 31, 2021, McNamara, Robert. (2021, July 31). The Missouri Compromise. Retrieved from McNamara, Robert. "The Missouri Compromise." ThoughtCo. (accessed June 3, 2023).