Once the St. Croix River was unambiguously identified following a commission provided by Jay's Treaty of 1794, it became clear that Machias Seal Island, as well as Grand Manan Island, was within 20 leagues ( 60 nautical miles ) of the shores of the United States and south of the line drawn due east from the mouth of the St. Croix River, but it remained unclear whether they were within the defined limits of Nova Scotia.