The seeds for the border disagreement were sown before Canada even existed as an independent nation, back when the Russian Empire still owned Alaska. In the 1825 Treaty of Saint Petersburg, Russia and the United Kingdom agreed to use the 141st meridian as the dividing line between Alaska and the northwestern section of British North America. But there was little concern over the maritime border for two main reasons. First, international law at that time allowed coastal states to control only the area three nautical miles from their coastline. Any differences in how the sea was to be divided were not seen as significant. There was also very little economic incentive for either side to try to exploit the region’s resources, as the sea was frozen for much of the year, making access difficult.

Complicating the issue was the language of the 1825 treaty. It was customary at the time to use French — and what was written was confusing and open to interpretation. Even when Russia sold Alaska to the U.S. in 1867, the issue of the maritime boundary did not attract any real attention.

But tensions over that boundary surfaced in the late 1970s.

Both states knew the Beaufort Sea probably contained significant sources of oil and gas. The U.S. discovery of large deposits of oil off the north slope of Alaska in 1968 generated unprecedented interest in the region. The two nations suspected the Beaufort Sea would also contain rich deposits.

In 1973, negotiations began for what would become the United Nations Convention on the Law of the Sea. As negotiations went on, it became clear that areas extending into the ocean from coastal states would be expanded from three to 200 nautical miles through the creation of exclusive economic zones. The convention gave all coastal states sovereign control over their EEZ’s resources. In 1977, both Canada and the United States applied this new 200-nautical-mile EEZ to their northern waters.

But given the 1825 treaty’s vagueness, they had differing interpretations of what that would look like. Canada claimed the boundary dividing Alaska from the Yukon and northern British Columbia should be extended in a straight line into the sea. The United States made the case for the “equidistance principle,” which meant drawing a line that extended perpendicular to the coastline. Unsurprisingly, both countries favoured themselves. The difference between the two created a 21,197-square-kilometre wedge of disputed water and seabed.

They tried to negotiate. In the first phase of negotiations in 1977, Canada suggested the two countries resolve several maritime disputes in one fell swoop, aiming to find compromises that could satisfy both nations. They told the U.S. that Canada would “accept a compromise jurisdictional boundary [in the Beaufort Sea] more or less along the geographic coordinates put forth by the United States, provided American officials would grant Canada similar boundary concessions in the Gulf of Maine and off the Strait of Juan de Fuca.” But the Americans refused to link the boundary issues in a comprehensive approach.

Further negotiations took place but never succeeded. The most recent effort was announced on September 24, 2024, renewing hope that this issue would be resolved once and for all, especially in an era of a rapidly changing Arctic. “Our common interests in the region have served as the foundation of our bilateral Arctic relations for many decades and will continue to guide our Arctic cooperation in the future,” read the joint statement by the two governments.