An Act of Admission of the State of Maine into the Union, March 3, 1820
The Act of Admission of the State of Maine into the Union, passed by the U.S. Congress on March 3, 1820, officially separated Maine from Massachusetts and established it as the new 23rd state. This Act formalized Maine's transition from a district of Massachusetts to a sovereign state within the United States. The Act of Admission was passed as part of the Missouri Compromise, which also admitted Missouri as a slave state.