Maine () is the northeasternmost state in the Lower 48 of the United States. Maine is the 12th-smallest by area, the 9th-least populous, and the 13th-least densely populated of the 50 U.S. states. It is in New England, bordered by New Hampshire to the west, the Atlantic Ocean to the southeast, and the Canadian provinces of New Brunswick and Quebec to the northeast and northwest, respectively. Maine is the only state to border only one other state, is the easternmost among the contiguous United States, and is the northernmost state east of the Great Lakes.

Maine is known for its jagged, rocky coastline; low, rolling mountains; heavily forested interior; picturesque waterways; and its seafood cuisine, especially lobster and clams. There is a humid continental climate throughout most of the state, including coastal areas. Maine’s most populous city is Portland, and its capital is Augusta.

For thousands of years after the glaciers retreated during the last Ice Age, indigenous peoples were the only inhabitants of the territory that is now Maine. At the time of European arrival, several Algonquian-speaking peoples inhabited the area. The first European settlement in the area was by the French in 1604 on Saint Croix Island, by Pierre Dugua, Sieur de Mons. The first English settlement was the short-lived Popham Colony, established by the Plymouth Company in 1607. A number of English settlements were established along the coast of Maine in the 1620s, although the rugged climate, deprivations, and conflict with the local peoples caused many to fail.

As Maine entered the 18th century, only a half dozen European settlements had survived. Loyalist and Patriot forces contended for Maine’s territory during the American Revolution. During the War of 1812, the largely undefended eastern region of Maine was occupied by British forces with the goal of annexing it to Canada via the Colony of New Ireland, but returned to the United States following failed British offensives on the northern border, mid-Atlantic and south which produced a peace treaty that restored the pre-war boundaries. Maine was part of the Commonwealth of Massachusetts until 1820 when it voted to secede from Massachusetts to become a separate state. On March 15, 1820, under the Missouri Compromise, it was admitted to the Union as the 23rd state.