Missouri Compromise

Definition

Harrison W. Mark
by
published on 05 June 2025
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Map of the United States on the Eve of Civil War, 1861 (by Simeon Netchev, CC BY-NC-ND)
Map of the United States on the Eve of Civil War, 1861
Simeon Netchev (CC BY-NC-ND)

The Missouri Compromise of 1820 was an effort by the US Congress to resolve a sectional dispute between the 'free states' of the North and the 'slave states' of the South. Hoping to hinder the westward expansion of slavery – and thereby limit the undue political influence of the slave-holding South – Northern representatives had sought to deny Missouri admittance into the Union unless it limited slavery within its borders. This was hotly opposed by Southern representatives, leading to the compromise: Missouri would enter the Union as a 'slave state' in exchange for the admittance of Maine as a 'free state', as well as the prohibition of slavery in all western lands north of the 36°30′ parallel, excluding Missouri itself. While this provided a temporary solution, the question of slavery would only become more contested, eventually leading to the American Civil War (1861-1865).

Background: An Empire of Slavery

By 1815, 1.4 million men, women, and children languished in a state of perpetual and hereditary bondage in the United States, the legal property of their masters. The institution of slavery was an undoubtedly hideous blight on what President Thomas Jefferson (1743-1826) had once called the 'empire of liberty'; indeed, in the years that followed the American Revolution (1765-1789) many White Americans recognized that slavery was incompatible with the Enlightenment ideals upon which their country was founded, summed up by the famous phrase 'all men are created equal'. Some slaveholders, like Jefferson himself, agreed that slavery was a moral evil but were worried that a general emancipation would have grave consequences – not only would the immediate release of all slaves threaten the White supremacy from which the slave-holding class derived its power, but it could also provoke insurrection, as some of the former slaves might seek retaliatory vengeance on their erstwhile masters. Poorer White Americans were also unwilling to be taxed so that the slaveholders could be compensated for freeing their slaves.

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Slaveholders claimed that they were paternalistic caretakers who treated their slaves better than Northern industrialists treated their wage workers.

And so, the Founders reluctantly sanctioned slavery, but with the implicit understanding that it would be gradually eradicated over time. Their commitment to this goal was manifest in several pieces of legislation – in 1787, Congress passed the Northwest Ordinance, which prohibited the expansion of slavery into the vast Northwest Territory, and the trans-Atlantic slave trade was abolished in 1807. The regulation of slavery in areas where it already existed was left to the states, but even here, there were great strides toward emancipation. Pennsylvania and the states of New England had already abolished slavery during the Revolution, while New York and New Jersey each began processes of gradual emancipation around the turn of the century. Diversified methods of farming in the Upper South left that region less dependent on slavery, causing an increased rate of individual slaveholders freeing their slaves in Delaware, Maryland, and Virginia. By the end of the 18th century, the institution of slavery was on decline everywhere in the United States except South Carolina and Georgia. Racism, of course, was still prevalent, and free Blacks were rarely regarded as equal. But there was still reason to hope that within only a few generations, slavery would have died a natural death, a bleak chapter in the otherwise glowing history of Jefferson's 'empire of liberty'.

But it was not long before this wave of emancipation came to an abrupt and screeching halt. The destruction wrought by the Napoleonic Wars (1804-1815) in Europe had disrupted international commerce for nearly a generation and had prevented the mass marketing of products like cotton. In the American South, where the climate was ideal for cotton growth, planters seized the opportunity to pick up the slack. By 1820, the United States had replaced India as the largest cotton producer in the world and would provide 68% of the world's cotton by 1850. But cotton cultivation was a labor-intensive process, even after the invention of the cotton gin; consequently, the interstate slave trade roared to life again, as planters rushed to buy slaves to toil on their cotton plantations. To justify this reversal, slaveholders no longer claimed that slavery was a moral evil. Instead, they claimed that they were paternalistic caretakers who treated their slaves better than Northern industrialists treated their wage workers.

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The Cotton Pickers by Winslow Homer
The Cotton Pickers by Winslow Homer
Winslow Homer (Public Domain)

More and more White settlers travelled west with their slaves, headed for the cotton-friendly regions of the southwestern Louisiana Purchase. In 1812, the state of Louisiana joined the Union as a 'slave state,' and just like that, the westward spread of slavery increased its momentum. Though there was not yet a clear distinction between the 'free states' of the North and the 'slave states' of the South – many Northern states were still in the process of weaning off slavery – the cultural differences between the two regions were already beginning to take shape. The industrializing North and the agrarian South had been feuding over the soul of the nation since the days of Alexander Hamilton and Thomas Jefferson's arguments in President George Washington's cabinet meetings. But now, the institution of slavery festered beneath the nation's surface like a tumor, poised to spread throughout the body of the nation – the only question was whether the nation would ignore it until it was too late.

Missouri Controversy & Tallmadge Amendment

At the end of the War of 1812 (1812-1815), the United States entered a period of peace and political stability known as the 'Era of Good Feelings'. Victory over a superior British army at the Battle of New Orleans (8 January 1815) had given Americans a new self-confidence as a nation, while the continued flood of White settlers into the uncharted West added new territories and states to the ever-growing 'empire of liberty'. By early 1819, enough people had settled in the Missouri Territory to qualify it for statehood. As was procedure, an 'enabling act' was introduced to Congress, which, if passed, would allow Missouri voters to elect delegates to begin drafting a state constitution. But on 13 February 1819, as the House of Representatives considered the act, a congressman from Poughkeepsie, New York, stood up and "tossed a bombshell into the Era of Good Feelings" (Howe, 147).

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James Tallmadge, Jr. (1778-1853) was a political outsider with a history of opposing slavery. In 1817, he had played an important role in speeding up the gradual emancipation of slaves in his home state, and the following year, he had objected to the admission of Illinois into the Union since its constitution had not provided enough evidence that it would adhere to the prohibition of slavery as laid out in the Northwest Ordinance. Now, Tallmadge introduced an amendment to the 'enabling act' that he believed should be conditional for Missouri's statehood: future importation of slaves into Missouri must be banned, and all slaves born in Missouri after its admission into the Union must be freed once they reach the age of 25. Currently, there were an estimated 10,000 enslaved people in Missouri, and Tallmadge's plan would lead to a peaceful abolition of slavery in the territory within a few generations. From a taxpayer's point of view, the amendment had the added benefit of not requiring financial compensation for slaveholders, since it would not free anyone who was currently enslaved.

James Tallmadge, Jr.
James Tallmadge, Jr.
Jeremiah Nims (Public Domain)

Tallmadge found a deal of support from his fellow Northerners, many of whom were already growing apprehensive about the admittance of more 'slave states' into the Union – the 'three-fifths' clause in the Constitution, which counted three-fifths of a state's enslaved population for representational purposes, granted the South undue influence that was disproportionate to its voting population. As a result, the South obtained several significant legislative and electoral victories in recent years that it otherwise would not have. Northern representatives rallied around Tallmadge's amendment in the hopes of ending the political supremacy of the slave-holding Southern states – to garner support, they made moral, religious, and economic appeals against the institution of slavery, and even quoted the Declaration of Independence. The Founders had always intended to eradicate slavery eventually, Tallmadge and his supporters argued. Now was the time to hurry that process along.

But the Southern representatives were unmoved. Indeed, even the aged Jefferson, living in retirement on his plantation of Monticello, added his voice to the Southern chorus denouncing the amendment. Congress could not force a state to emancipate its slaves, they argued; such an act would surely violate the Constitution. And so, the lines had been drawn for the fiery conflict that would divide the nation for decades to come and culminate in civil war. This outcome was foreseen by Rep. Thomas W. Cobb of Georgia, who told Tallmadge, "You have kindled a fire which all the waters of the ocean cannot put out, which seas of blood can only extinguish." Tallmadge, convinced of the righteousness of his cause, cooly replied, "If a dissolution of the Union must take place, let it be so! If civil war, which gentlemen so much threaten, must come, I can only say, let it come!" (quoted in Howe, 148).

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The Compromise

The Tallmadge Amendment was approved in the House of Representatives, where the Northerners had an advantage, by a margin of 87-76. But thanks to the three-fifths clause, the South had greater strength in the Senate; three of the four senators from Illinois and Indiana joined with their Southern colleagues to defeat the bill. So, with the two houses deadlocked, the Missouri statehood bill lapsed as Congress adjourned for the summer. In the following months, both sides tried to whip up support from their constituents. Senator Rufus King (1755-1827) of New York, the last icon of the dying Federalist Party, gave speeches denouncing the three-fifths clause and supporting the Tallmadge Amendment, for which he was accused of fanning the flames of sectionalism. Jeffersonian Republicans, both in the South and in Washington, D.C., claimed that the anti-Missouri proponents were merely disgruntled political outsiders who wanted to split the party.

The Compromise showed that the South was much more unified behind the institution of slavery than was previously believed.

The administration of President James Monroe (served 1817-1825) was not idle during this time. Hoping to resolve the Missouri issue, Monroe met with the Speaker of the House, Henry Clay (1777-1852) of Kentucky, and several Senate leaders to devise a plan. In June, the Massachusetts legislature had voted to separate from the District of Maine, which was now eligible for statehood – might Maine be admitted as a 'free state' in exchange for the admission of Missouri without the Talmadge Amendment? When the next Congress convened in December 1819, this proposal was presented to the Senate, which found it to be agreeable. In early 1820, it voted to pass a bill that would admit Maine into the Union as a 'free state', with an amendment that the people of Missouri could form a state constitution without restrictions on slavery.

But before this bill could be sent back to the House, Senator Jesse B. Thomas of Illinois rose to introduce a second amendment. Though Thomas himself had previously voted with the pro-slavery bloc, he knew that many Northerners would not be satisfied with the bill in its current state. So, he added the proviso that slavery would be banned in the territories of the Louisiana Purchase north of 36°30' north latitude – the southern boundary of Missouri – with the sole exception of Missouri itself. The so-called 'Thomas Proviso' was approved by the Senate, and Speaker Clay skillfully guided the whole package through the House, engineering separate votes on each of the issues. On 5 March 1820, Congress passed the Missouri Compromise, which included: the admission of Maine as a 'free state', the admission of Missouri as a 'slave state,' and the abolition of slavery in all western territories north of Missouri's southern border, save for the land within Missouri itself. President Monroe – who said he would have vetoed the Tallmadge Amendment – was satisfied with the Thomas Proviso and signed the bill on 6 March.

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Aftermath

As historian Daniel Walker Howe points out, the Missouri Compromise had multiple outcomes. First, it ensured the breakup of the Democratic-Republican Party along sectional lines, leading to the end of the relative political unity that had characterized the 'Era of Good Feelings'. Second, it confirmed the growing power of the US Senate, which had traditionally been less influential than the House of Representatives but had in this instance been the more instrumental chamber. Third, it enhanced the national reputation of Henry Clay, who reaped the lion's share of the credit for the compromise and would go on to dominate national politics over the next several decades.

Henry Clay, 1818
Henry Clay, 1818
Matthew Harris Jouett (Public Domain)

But by far the most significant outcome of the compromise was that it showed that the South was much more unified behind the institution of slavery than was previously believed. Gone was the idyllic notion that the 'peculiar institution' would die out on its own – even Jefferson, who had once professed to believe in the gradual abolition of slavery, now sided with the men who supported its expansion. From here, the issue of slavery would only become more divisive as it dominated the political conversation in the United States. Jefferson, who was in the twilight years of his life and would not live to see the nation torn apart by civil war, nevertheless predicted that the question of slavery would only be resolved by violence:

This momentous question, like a fire bell in the night, awakened and filled me with terror. I considered it at once the knell of the union. It is hushed, indeed, for the moment. But this is a reprieve only, not a final sentence…I regret that I am now to die in the belief, that the useless sacrifice of themselves by the generation of 1776, to acquire self-government and happiness to their country, is to be thrown away by the unwise and unworthy passions of their sons, and that my only consolation is to be, that I may not live to weep over it.

(quoted in Howe, 157).

Indeed, it did not take long for the volatility of the Missouri Compromise to become apparent. When the Missourians gathered to draft their state constitution, they not only legalized slavery in perpetuity, but also forbade free Blacks and Mulattoes from "coming to and settling in this state" (ibid). This directly contradicted the US Constitution, since some free Blacks were citizens of other states and were therefore guaranteed the same 'privileges and immunities' in every state. When the Missouri state constitution was sent to Congress for approval, many Northern congressmen threatened to oppose it, which would undo all the progress of the Missouri Compromise.

It was once again left to Clay to diffuse the situation by offering what became known as the 'Second Missouri Compromise': Congress would approve the Missouri state constitution, provided the Missouri legislature not pass any law violating the rights of free Black citizens. This was agreed to, and Missouri officially entered the Union as the 24th state in August 1821; Maine had already been admitted. The trend set by the Missouri Compromise – the admittance of one 'free state' for every 'slave state,' and vice versa – would continue until it was challenged by the Compromise of 1850 and ultimately repealed four years later in the Kansas-Nebraska Act. Far from providing a permanent solution, the Missouri Compromise only delayed the conflict that would eventually boil over into the American Civil War.

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About the Author

Harrison W. Mark
Harrison Mark is a graduate of SUNY Oswego, where he studied history and political science.

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Questions & Answers

What led to the Missouri Compromise?

The Missouri Compromise of 1820 was an attempt by the US Congress to settle a sectional dispute between the 'free states' of the North and the 'slave states' of the South, concerning the spread of slavery into the state of Missouri.

What was the Missouri Compromise?

In the Missouri Compromise, it was decided that Missouri would join the Union as a 'slave state' in exchange for the admission of Maine as a 'free state.' It was also decided that slavery would be prohibited in all western territories north of the 36°30′ parallel, excluding Missouri itself.

Why was the Missouri Compromise important?

The Missouri Compromise was important for turning the question of slavery into the most important national issue, and for setting the divide between the 'free states' of the North and the 'slave states' of the South at the 36°30′ parallel.

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Mark, H. W. (2025, June 05). Missouri Compromise. World History Encyclopedia. Retrieved from https://www.worldhistory.org/Missouri_Compromise/

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Mark, Harrison W.. "Missouri Compromise." World History Encyclopedia. Last modified June 05, 2025. https://www.worldhistory.org/Missouri_Compromise/.

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Mark, Harrison W.. "Missouri Compromise." World History Encyclopedia. World History Encyclopedia, 05 Jun 2025, https://www.worldhistory.org/Missouri_Compromise/. Web. 13 Jun 2025.

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