Congress passes a law admitting the state of Vermont to the Union, effective 4 March, after that state had existed for 14 years as a de facto independent largely unrecognized state.

Admission to the Union is provided by the Admissions Clause of the United States Constitution in Article IV, Section 3, Clause 1, which authorizes the United States Congress to admit new states into the Union beyond the thirteen states that already existed when the Constitution came into effect. The Constitution went into effect on June 21, 1788, in the nine states that had ratified it, and the U.S. federal government began operations under it on March 4, 1789, when it was in effect in 11 out of the 13 states. Since then, 37 states have been admitted into the Union. Each new state has been admitted on an equal footing with those already in existence.

Vermont is a state in the New England region of the Northeastern United States. It borders Massachusetts to the south, New Hampshire to the east, New York to the west, and the Canadian province of Quebec to the north. According to the most recent U.S. Census estimates, the state has an estimated population of 648,493, making it the second-least populated of all U.S. states. It is the nation's sixth smallest state in area. The state's capital of Montpelier is the least populous U.S. state capital. No other U.S. state has a most populous city with fewer residents than Burlington.

The Vermont Republic, officially known at the time as the State of Vermont, was an independent state in New England that existed from January 15, 1777, to March 4, 1791. The state was founded in January 1777, when delegates from 28 towns met and declared independence from the jurisdictions and land claims of the British colonies of Quebec, New Hampshire, and New York. The republic remained in existence for the next fourteen years, albeit without diplomatic recognition from any foreign power. On March 4, 1791, it was admitted into the United States as the State of Vermont, with the constitution and laws of the independent state continuing in effect after admission.