Belfast is a city in Waldo County, Maine, in the United States. As of the 2010 census, the city population was 6,668. Located at the mouth of the Passagassawakeag River estuary on Belfast Bay and Penobscot Bay. Belfast is the county seat of Waldo County. The seaport has a wealth of antique architecture in several historic districts, and remains popular with tourists.
The area was once territory of the Penobscot tribe of Abenaki Native Americans, which each summer visited the seashore to hunt for fish, shellfish and seafowl. In 1630, it became part of the Muscongus Patent, which granted rights for English trading posts with the Native Americans, especially for the lucrative fur trade. About 1720, General Samuel Waldo of Boston bought the Muscongus Patent, which had evolved into outright ownership of the land, and was thereafter known as the Waldo Patent.
Waldo died in 1759, and his heirs would sell the plantation of Passagassawakeag (named after its river) to 35 Scots-Irish proprietors from Londonderry, New Hampshire. Renamed Belfast after Belfast, Ireland, it was first settled in 1770, and incorporated as a town in 1773. The village was mostly abandoned during the Revolution while British forces occupied Bagaduce (now Castine).