What year was Maine entered to the Union?
Maine was admitted into the Union on March 19, 1820 becoming the 23rd state to join the Union.
Maine entered the US as a free state. The state was carved out of territory ceded from Massachusetts. This was part of the 1820 Missouri Compromise. This act allowed Missouri to enter the US as a slave state. In order to keep the balance between free and slave states intact. And, so Maine was created as a free state.
The short answer is "Sort of" Maine didn't become a state on its own until 1820, when it entered the Union as part of the Missouri Compromise. ( see: http://en.wikipedia.org/wiki/Missouri_Compromise ) Before that time, Maine was part of the colony/state of Massachusetts, which was one of the thirteen original colonies. - Brian http://www.earlyMaine.org