Fort Kent, Maine in the context of "Fulton Chain of Lakes"

The Saint John River (French: fleuve Saint-Jean; Maliseet-Passamaquoddy: Wolastoq) is a 673-kilometre-long (418 mi) river flowing within the Dawnland region from headwaters in the Notre Dame Mountains near the Maine-Quebec border through western New Brunswick to the northwest shore of the Bay of Fundy. Eastern Canada's longest river, its drainage basin is one of the largest on the east coast at about 55,000 square kilometres (21,000 sq mi). This “River of the Good Wave” and its tributary drainage basin formed the territorial countries of the Wolastoqiyik and Passamaquoddy First Nations (named Wolastokuk and Peskotomuhkatik, respectively) prior to European colonization, and it remains a cultural centre of the Wabanaki Confederacy to this day.

The Webster–Ashburton Treaty following the Aroostook War established a border between New Brunswick and Maine following 130 km (81 mi) of the river, while a tributary forms 55 km (34 mi) of the border between Quebec and Maine. Maine communities along the river include Fort Kent, Madawaska, and Van Buren. New Brunswick settlements through which it passes include, moving downstream, Edmundston, Fredericton, Oromocto, and Saint John.

Aroostook County (/əˈruːstək, -ˈrʊs-/ ə-ROOSS-tək, -⁠RUUSS-; French: Comté d'Aroostook) is the northernmost county in the U.S. state of Maine. It is located along the Canada–United States border. As of the 2020 census, the population was 67,105. The county seat is Houlton, with offices in Caribou and Fort Kent.

Known in Maine as "The County", it is the largest county in Maine by total area, the second-largest in the United States east of the Mississippi River by total area (behind St. Louis County, Minnesota), and the 31st-largest county in the entire contiguous U.S. With over 6,800 square miles (18,000 km) of land, it is larger than three of the smaller U.S. states. The state's northernmost village, Estcourt Station, is also the northernmost community in the New England region and in the contiguous United States east of the Great Lakes.

U.S. Route 1 or U.S. Highway 1 (US 1) is a major north–south United States Numbered Highway that serves the East Coast of the United States. It runs 2,370 miles (3,810 km) from Key West, Florida, north to Fort Kent, Maine, at the Canadian border, making it the longest north–south road in the United States. US 1 is generally paralleled by Interstate 95 (I-95), though US 1 is significantly farther west and inland between Jacksonville, Florida, and Petersburg, Virginia, while I-95 is closer to the coastline. In contrast, US 1 in Maine is much closer to the coast than I-95, which runs farther inland than US 1. The route connects most of the major cities of the East Coast from the Southeastern United States to New England, including Miami, Jacksonville, Augusta, Columbia, Raleigh, Richmond, Washington, D.C., Baltimore, Philadelphia, Newark, New York City, New Haven, Providence, Boston, and Portland.

While US 1 is generally the easternmost of the main north–south U.S. Routes, parts of several others occupy corridors closer to the ocean. When the road system was laid out in the 1920s, US 1 was mostly assigned to the existing Atlantic Highway, which followed the Atlantic Seaboard Fall Line between the Piedmont and the Atlantic Plain north of Augusta, Georgia. At the time, the highways farther east were of lower quality and did not serve the major population centers. From Henderson, North Carolina, to Petersburg, Virginia, it is paralleled by I-85. Construction of the Interstate Highway System gradually changed the use and character of US 1, and I-95 became the major north–south East Coast highway by the late 1960s.