Maine, state in northern New England in the United States. It is bounded by the Canadian provinces of Québec on the northwest and New Brunswick on the northeast. To the southwest lies New Hampshire, and to the southeast, the Atlantic Ocean. Maine entered the Union on March 15, 1820, when it was separated from Massachusetts to form the 23rd state. The name Maine probably originated as the word used by English explorers to refer to the mainland; it may also be derived from the province and region of Maine in northwestern France. Augusta is Maine’s capital. Portland is the largest city.