The Missouri Compromise of 1820

March 6, 1820

The Missouri Compromise comprised legislation passed by the U.S. Congress in 1820 that attempted to resolve sectional disputes over the extension of slavery in western territories of the United States.

Henry Clay, Illustration, c 1835, LOC

Henry Clay is often given credit for the passage Missouri Compromise because he used his considerable influence as Speaker of the House of Representatives to forge a consensus in Congress. Image Source: Library of Congress.

What Was the Missouri Compromise?

The Missouri Compromise of 1820 was an agreement that temporarily resolved growing sectional tensions between the North and the South, which lingered since the Constitutional Convention of 1787.

Following prolonged debates at the Constitutional Convention, a series of compromises emerged, enabling the formation of a “more perfect Union.” While these compromises expedited the establishment of the new republic, they also laid the groundwork for future conflicts over the issue of slavery, particularly as the nation expanded westward.

The Northwest Ordinance of 1787 played a pivotal role by prohibiting slavery in territories north of the Ohio River, temporarily quelling sectional disputes. However, the 1803 Louisiana Purchase introduced fresh challenges, compelling Congress to grapple with slavery’s expansion into this vast territory.

Thomas Jefferson, Painting, Rembrandt Peale
Thomas Jefferson was an advocate for the abolition of slavery in the Northwest Territory. As President, he authorized the Louisiana Purchase. Image Source: Wikipedia.

In 1812, the Missouri Territory was carved out of the Louisiana Purchase, attracting settlers, including slaveholders from the South. When Missouri sought statehood in 1818, it had a substantial slave population. The introduction of the Tallmadge Amendment in 1819 aimed to restrict slavery in Missouri, triggering intense debates in Congress. The House approved a bill recommending Missouri’s statehood with the amendment, but the Senate did not vote on it.

In 1820, Congress revisited the issue and reached a compromise. This compromise combined legislation for Maine’s admission as a free state with an amendment enabling Missouri’s entry as a slave state, preserving equal Senate representation. Importantly, it established a line at 36°30′ north latitude, prohibiting slavery north of Missouri’s southern border within the Louisiana Territory.

The Missouri Compromise, signed into law by President James Monroe in March 1820, temporarily quelled the slavery debate, though it did not resolve underlying tensions. It also set a precedent for congressional regulation of slavery in territories, foreshadowing future conflicts and ultimately contributing to the nation’s devastating Civil War.

Subsequent events, including the Compromise of 1850 and the Kansas-Nebraska Act of 1854, would further fuel these sectional tensions, leading to the war that determined the fate of the Union and slavery in the United States.

Missouri Compromise History

When delegates to the Constitutional Convention assembled in Philadelphia in 1787, one of the more daunting tasks that they faced was resolving sectional differences between the North and South centered on the issue of slavery.

After weeks of debate proved futile, the delegates negotiated a series of compromises that enabled them to proceed with their primary assignment of forming “a more perfect Union” between the separate states.

In the short term, the compromises regarding the status of slavery established in the Constitution facilitated the creation of the new republic — at the expense of blacks held in bondage — but they also sowed the seeds of turmoil that began coming to fruition as the nation expanded west in the coming decades.

The Northwest Ordinance Abolishes Slavery in the Northwest Territory

As the delegates to the Constitutional Convention set about creating a new government, representatives to the Congress of the existing government established under the Articles of Confederation, known as the Confederation Congress, were meeting in New York.

On July 13, 1787, the Confederation Congress enacted the Northwest Ordinance, which stipulated “There shall be neither slavery nor involuntary servitude in the said territory… ”

The Northwest Ordinance established the Ohio River as the border separating free and slave states between the Appalachian Mountains and the Mississippi River. For the next three decades, that boundary forestalled major sectional disputes over slavery.

Nathaniel Gorham, Portrait, Peale
This painting by Charles Willson Peale depicts Nathaniel Gorham, who was President of Congress when the Northwest Ordinance of 1787 was enacted. Image Source: Wikipedia.

The Louisiana Purchase Expands the United States

Circumstances changed in 1803 when Napoleon Bonaparte sold President Thomas Jefferson 828,000 square miles of land west of the Mississippi River. The Louisiana Purchase created new challenges for the federal government. Besides land ownership issues regarding the native inhabitants, Congress eventually had to address the question of the expansion of slavery in the new territory.

The Missouri Territory Attracts Southern Slaveowners

In 1812, Congress carved the Missouri Territory out of the Louisiana Purchase. Soon after, settlers began pouring into the new territory, and many of them were slaveholders from the South. 

In 1818, when the residents of Missouri petitioned Congress for statehood, roughly 8,000 to 10,000 slaves lived in the territory.  In January, residents of the territory petitioned the U.S. House of Representatives for statehood, but the House did not consider the measure during that session.

In December 1818, Missouri residents petitioned Congress for statehood a second time.

The Tallmadge Amendment Proposes Gradual Emancipation for Missouri

The House took up the request during the next session. Southerners expected Congress to admit Missouri as a slave state, but on February 13, 1819, New York Congressman James Tallmadge introduced an amendment to the Missouri statehood measure that would gradually end slavery in the new state.

The Tallmadge Amendment also mandated the emancipation of all children of slaves born in the State of Missouri upon reaching the age of twenty-five. The Tallmadge Amendment started a year of bitter debate in both houses of Congress. 

On February 17, 1819, the House passed a bill recommending Missouri statehood, including the Tallmadge Amendment, by a vote of 82 to 78, and forwarded it to the Senate. The upper chamber never voted on the proposed legislation.

Henry Clay Brokers the Missouri Compromise

During the following session of Congress, on January 3, 1820, the House passed legislation to admit Maine to the Union as a free state.

Later that month, the lower chamber revisited the proposal for Missouri statehood. On January 26, 1820, John W. Taylor of New York introduced an amendment allowing Missouri to enter the union as a slave state, which the House adopted.

The Senate tied the two bills together, passing a single bill admitting Maine to the Union and an amendment enabling the people of Missouri to draft a state constitution. The proposed legislation hinged upon an important second amendment introduced by Senator Jesse B. Thomas of Illinois.

The original bill provided for a trade-off — admitting Maine as a free state in return for admitting Missouri as a slave state, thus maintaining the balance of power in the Senate — 12 free states and 12 slave states.

As amended by Thomas, however, the bill also prohibited slavery in the rest of the Louisiana Territory, north of the southern border of the new state (36°30′ north latitude). The Senate passed the amended legislation and returned it to the House.

The amended Senate bill evoked considerable sectional rancor in the lower chamber.

House Speaker Henry Clay had to use his considerable skills to forge a consensus. Eventually, he got his colleagues to enact two bills — one admitting Maine to the Union and another, which included the Thomas Amendment, enabling the citizens of Missouri to draft a state constitution with no restrictions upon slavery.

Together, the two pieces of legislation became known as the Missouri Compromise.

Congress passed the compromise legislation on March 5, 1820, and President James Monroe signed it into law the next day.

A Second Compromise for Missouri

Missouri’s statehood request required a second compromise after Missouri submitted its state constitution to Congress in 1821.

The proposed constitution contained a provision that excluded “free negroes and mulattoes” from the state.

Once again, Clay demonstrated his abilities as the “Great Compromiser” by getting Congress to allow the admission of Missouri to the Union provided that the exclusionary clause in the proposed constitution “shall never be construed to authorize the passage of any law . . . by which any citizen of either of the States in this Union shall be excluded from the enjoyment of any of the privileges and immunities to which such citizen is entitled under the Constitution of the United States.”

Thus, by agreeing to never deny citizens of other states coming into Missouri, the rights afforded them by the U.S. Constitution, Missouri became the 24th state on August 10, 1821.

Missouri Compromise Outcome and Effects

Besides settling the issues at hand, namely the admission of the states of Missouri and Maine to the Union, the Missouri Compromise had other important consequences.

  • It temporarily muffled the debate over slavery (or at least the extension of slavery) in the United States, although the abolitionist movement continued to grow in the North.
  • It also established the precedent that Congress could regulate slavery in the territories even though the Constitution did not address the issue.

Three decades later, that precedent became the focal point of constitutional and states’ rights arguments that contributed to the attempted dissolution of the Union in 1860.

Missouri Compromise Aftermath

The slavery issue reached crisis proportions once again in 1850 when Congress struggled over the disposition of new territories acquired during the Mexican-American War.

The Compromise of 1850, authored by Clay and shepherded through Congress by Illinois Senator Stephen Douglas, formally codified the concept of popular sovereignty, which Douglas and Michigan Senator Lewis Cass championed.

Stephen Douglas, Portrait
Stephen Douglas. Image Source: Wikipedia.

In 1854, the Kansas-Nebraska Act — which also invoked popular sovereignty — gutted the key provision of the Missouri Compromise regarding slavery in the Missouri Territory.

Three years later, the U.S. Supreme Court’s decision in the case of Dred Scott v. Sandford, nurtured the growth of the Republican Party, alienating Southerners even more.

The election of Abraham Lincoln to the presidency in 1860, proved to be the death knell of the spirit of compromise.

Ultimately, only the tragedy of four years of civil war would determine the future of the Union, and slavery in the United States.

Missouri Compromise Significance

The Missouri Compromise of 1820 was important to the history of the United States for various reasons:

  1. It temporarily eased the growing sectional tensions between the North and the South over the issue of slavery. By balancing the admission of Maine as a free state and Missouri as a slave state, it maintained equal representation in the Senate, preventing an immediate crisis.
  2. The compromise set a boundary, marking 36°30′ north latitude, where slavery was prohibited within the Louisiana Territory north of Missouri’s southern border. This marked the first time Congress actively regulated slavery in newly acquired territories, setting a precedent for future legislative actions.
  3. The Missouri Compromise provided a brief pause in the slavery debate, allowing the nation to focus on other issues. However, it did not address the fundamental question of slavery’s expansion, which would resurface in subsequent years and ultimately lead to the American Civil War.

The Missouri Compromise marked a critical moment in the nation’s history, foreshadowing the turbulent events that would follow in the decades leading up to the Civil War.

Missouri Compromise APUSH, Review, Notes, Study Guide

Use the following links and videos to study the Missouri Compromise of 1820, the Secession Crisis, and the Civil War for the AP US History Exam. Also, be sure to look at our Guide to the AP US History Exam.

Missouri Compromise APUSH Definition

The Missouri Compromise was an agreement reached in 1820 between Northern and Southern states in the United States that admitted Missouri as a slave state and Maine as a free state. It established the 36°30′ parallel as the dividing line between slave states and free states in the Louisiana Purchase Territory. The compromise was seen as a temporary solution to the issue of slavery expansion, but it ultimately contributed to the growing tensions between North and South that led to the Civil War.

Missouri Compromise Video for APUSH Notes

This video from Daily Bellringer discusses the Missouri Compromise.

Citation Information

The following information is provided for citations.

  • Article Title The Missouri Compromise of 1820
  • Date March 6, 1820
  • Author
  • Keywords Missouri Compromise, Jesse Burgess Thomas, Henry Clay, James Tallmadge, John W. Taylor
  • Website Name American History Central
  • Access Date February 27, 2024
  • Publisher R.Squared Communications, LLC
  • Original Published Date
  • Date of Last Update October 27, 2023

The Missouri Compromise of 1820 is Part of the Following on AHC