The Northwest Angle is a small part of northern Minnesota that is the only part of the United States outside of Alaska that is north of the 49th parallel. That parallel is the northern boundary of the 48 contiguous states extending eastward from the west coast along the northern boundaries of Washington, Idaho, Montana, North Dakota, and part of Minnesota to the Northwest Angle. Further east, the U.S.A. does not extend that far north. Map projections sometimes create an optical illusion that Maine extends further north than that; that illusion does not occur in maps in which parallels of latitude are straight lines. Like Alaska, the Northwest Angle cannot be reached from the rest of the USA without either going through Canada or crossing water -- specifically, the Lake of the Woods.
The Treaty of Paris (1783), concluded between the United States and Britain at the end of the American Revolutionary War, stated that the boundary between the U.S.A. and the British possessions to the north would run "...through the [Lake of the Woods] to the most northwesternmost point thereof, and from thence on a due west course to the river Mississippi..." The parties did not suspect that the source of the Mississippi, Lake Itasca, was south of that point. Consequently the Northwest Angle is the result of 18th-century ignorance of geography. In 1818 the error was corrected by having the boundary run due south from the northwest point of the lake to the 49th parallel and then westward along it. When this north-south line was surveyed, it was found to intersect other bays of the lake and therefore cut off a portion of U.S. territory, now known as the Northwest Angle.
The Northwest Angle has only about 100 inhabitants, and the border crossing is unstaffed. Travelers using the single gravel road into the Angle are expected to use the telephone provided to contact Canadian or U.S. customs and make their declarations.
