Which of the continental US states extends farthest north?

While states like Maine or Washington seem like logical contenders for the northernmost point in the contiguous United States, the distinction belongs to a small, peculiar piece of Minnesota. This isolated section, known as the Northwest Angle, is a sliver of land that juts northward into Canada, making it the only part of the Lower 48 to extend north of the 49th parallel.

This geographical oddity is the result of a mapping error dating back to the 1783 Treaty of Paris, which ended the American Revolutionary War. The treaty's text defined the border based on a line running from the northwesternmost point of the Lake of the Woods west to the source of the Mississippi River. However, the mapmakers were mistaken about the region's geography; the Mississippi's actual source lay much farther south, making their intended boundary line impossible.

Decades later, the Anglo-American Convention of 1818 established the 49th parallel as the primary border. To resolve the earlier treaty's error, surveyors simply dropped a line due south from the designated point on the Lake of the Woods until it intersected this new parallel. This fix inadvertently carved out the Northwest Angle, creating a practical exclave. To this day, residents and visitors can only reach this northernmost tip of the continental U.S. by land by first driving through Canada.