Northeast Boundary Dispute Northeast Boundary Dispute,
controversy between the United States and Great Britain
concerning the Maine–New Brunswick boundary. The treaty of 1783
ending the American Revolution had described the northeastern
boundary of the United States as running due north from the
source of the St. Croix River to the highlands dividing the St.
Lawrence River tributaries and the Atlantic Ocean, and along
those highlands to the northwesternmost head of the Connecticut
River. Disputes over that definition lasted almost 60 years. The
identity of the St. Croix was decided (1798) by a commission
created by Jay's Treaty (1794). However, as no mountain range
existed between the Atlantic and St. Lawrence systems, the
question was submitted to arbitration, in accordance with the
Treaty of Ghent (1814). The king of the Netherlands, as
arbitrator, designated the St. John River as the boundary
(1831), but this decision was not accepted by the United States.
In 1839 the dispute led to the so-called Aroostook