The United States Senate, A.D. 1850, by Robert E. White Church. Courtesy of the U.S. Senate Collection.



Not since 1788 had the meaning and interpretation of the United States Constitution been so intensely debated. Missouri’s admission was at the heart of a long-unanswered constitutional question: How should power be divided between the federal government and the states?

Congressmen were divided by whether they believed that Congress had the authority to place conditions — in this instance, a restriction on the spread of slavery in Missouri — on a state, even before it was admitted into the Union. Debates in Congress reached heated levels, as threats of disunion and even civil war became commonplace.


Since all the inhabitants of Missouri are against the prohibition of slavery, to insist on it is to entirely put it out of her power to enter the Union, and to keep her in a state of colonial tyranny.

~ Rep. Charles Pinckney, South Carolina

If you persist, the Union will be dissolved. You have kindled a fire which all the waters of the ocean cannot put out, which seas of blood can only extinguish.

~ Rep. Thomas W. Cobb, Georgia

An opportunity is now presented, if not to diminish, at least to prevent, the growth of a sin which sits heavy on the soul of every one of us.

~ Rep. Arthur Livermore, New Hampshire


In December 1819, Maine, which was then part of Massachusetts, formally requested admission into the Union. Kentucky Representative and Speaker of the House Henry Clay saw an opportunity to break the deadlock over Missouri by including Missouri and Maine in the same bill, balancing the representation of northern and southern states in the United States Senate.


Map of the State of Maine, 1820, by Moses Greenleaf. Courtesy of the Library of Congress.

The Thomas Amendment

In 1820, the U.S. House of Representatives passed a bill admitting Maine to the Union as a free state. The bill included an amendment authorizing the people of Missouri to form a constitution and state government without any restriction on slavery.

The Senate accepted the bill but added an amendment by Illinois Senator Jesse B. Thomas — who favored Missouri’s admission as a slave state — prohibiting slavery, with the exception of Missouri, in the remaining parts of the Louisiana Territory north of the 36°30 ́ latitude. Any future state below that latitude would enter the Union as a slave state. However, the House rejected all of the Senate's amendments, and a stalemate again defined Congressional attempts to admit Missouri.

Henry Clay

Clay served as both a United States Senator and Representative from Kentucky. He favored the admission of Missouri as a slave state and intervened to help several times during Missouri’s struggle for statehood. Because of his active involvement and ability to compromise, Clay would become widely known as the “Great Compromiser” or the “Great Pacificator.”

Henry Clay by Matthew Harris Jouett, 1818. Courtesy of Wikimedia Commons.

The Compromise

In order to break the deadlock in Congress, Speaker of the House Henry Clay formed a joint conference of members of the House and Senate and convinced the committee to reach a resolution that both chambers could accept.

1) Maine would enter the Union as a free state.

2) Missouri would be authorized to form a constitution and erect a state government with no restriction on slavery.

3) Slavery would be prohibited in the remaining parts of the Louisiana Territory north of the 36° 30 ́ latitude as proposed in the Thomas Amendment.

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"Missouri Compromise, 1820," created by Pea Pod Creative in partnership with Struggle for Statehood project team.

Did you know?

 The Missouri debates led to the creation of a commonly used word idiom: “bunk.” Congressional speeches had become so repetitive and boring, that when North Carolina Congressman Felix Walker demanded to make a speech on the behalf of his home county “Buncombe,” the House refused to listen. From this emerged the word “bunk”– meaning foolish talk or nonsense.