1. Maine was officially recognized as a state on September 17, 1819. The state was originally part of Massachusetts until it became its own entity.

2. The naval battle of Machias took place on September 17, 1777, during the American Revolutionary War. The battle was fought between British ships and American privateers from Machias, Maine. The American privateers were able to capture the British ship, Unity, after a fierce battle.

3. On September 17, 1973, Maine Senator Margaret Chase Smith introduced a resolution to establish National Grandparents Day. The resolution was passed by Congress and signed into law by President Jimmy Carter in 1978.

4. The Maine Supreme Judicial Court ruled on September 17, 1999, that same-sex couples could be granted some of the legal rights and benefits of marriage, but they would not be considered legally married. This ruling was a significant step forward for LGBTQ+ rights in Maine.

5. The first recorded frost of the season in Maine typically occurs in September. Many farms and gardens start to wind down for the winter, and residents begin to prepare for colder weather and shorter days.