In a remote pocket of Minnesota lies a small piece of land cut off from the rest of the state by water and connected to Canada by land. Known as the Northwest Angle, it exists today because 18th-century mapmakers misunderstood the geography of Lake of the Woods and the Mississippi River. That error reshaped the U.S. map.
A Border Drawn on a Flawed Map
In the 1783 Treaty of Paris, U.S. and British negotiators relied on the Mitchell Map, which inaccurately depicted the area’s rivers and lakes. The treaty set the border to run west from the “northwesternmost point” of Lake of the Woods to the Mississippi River—believed to be further north than it actually is.
Surveys and Settlements
Surveys in the 19th century revealed the Mississippi’s true source lay south of the lake. To fix the border, the 1818 Convention drew a new line from the lake’s northwest corner due north to the 49th parallel, then west. This left a wedge of U.S. land cut off by water.
An Exclave Is Born
This land—Angle Township—became the only part of the contiguous United States north of the 49th parallel. Isolated and forested, it has about 150 residents and is accessible only by traveling through Canada or across the ice of Lake of the Woods in winter.
Tucked between Canada and a vast northern lake, Minnesota’s Northwest Angle exists because of an 18th-century map error.
It’s the only spot in the contiguous U.S. above the 49th parallel, accessible by crossing a lake or driving through another country…🧵👇 pic.twitter.com/EYoQmGAogn
— Detective Tiger's Stories (@TigerDetective) May 5, 2025