Canada and the United States have one land dispute over Machias Seal Island (off the coast of Maine), and four other maritime disputes in the Arctic and Pacific. Although they share the longest international border in the world, the two countries have a long history of disputes about the border's demarcation (see Canada–United States border). Current disputes Machias Seal Island—about —and North Rock (Maine and New Brunswick), located in what is known as the "Grey Zone" (about in size), is occupied by a Canadian lighthouse but claimed by the United States and visited by U.S. tour boats. The area is patrolled by the Canadian and US Coast Guard, but only Canadian Coast Guard occupies the lighthouse. The unresolved maritime boundary breaks into two elements: the sovereignty of the island and the location of the maritime boundary taking into account who is the rightful owner of the island. Strait of Juan de Fuca (Washington state and British Columbia): At the mouth of the strait, both countries declared fishing zones in 1977. Each country used a mildly differing method to define an equidistant water boundary. The two separate water areas in dispute amount to about . Yukon–Alaska dispute, Beaufort Sea (Alaska and Yukon) Canada supports an extension into the sea of the land boundary between Yukon and Alaska. The U.S. does not, but instead supports a line equidistant with respect to the coastline. Such a demarcation means that a minor portion claimed by Canada as Northwest Territories Exclusive Economic Zone (EEZ) is also claimed by the US, because the EEZ boundary between Northwest Territories and Yukon follows a straight north-south line into the sea. The U.S. claims would create a triangular shaped EEZ for Yukon/Canada. The disputed area is about in size. The precise translation of a phrase in the Anglo-Russian Convention of 1825, which was written in French, is part of the issue. The convention makes reference to the 141st Meridian "in its prolongation as far as the Frozen ocean." The authentic text is in French: "dans son [sic] prolongation jusqu’à la Mer Glaciale." The precise question is the interpretation that should be given to the preposition "jusqu’à." Specifically, is it inclusive or exclusive of the object to which the preposition relates? Northwest Passage: Canada claims the passage as part of its "internal waters" belonging to Canada, while the United States regards it as an "international strait" (a strait accommodating open