Lake Superior contains a phantom island. After the American Revolution, the Treaty of Paris established the boundary between the United States and Canada as running “through Lake Superior northward of the Isles Royal and Phelipeaux to the Long Lake,” following an inaccurate map created by John Mitchell. In the 1820s surveyors discovered that Phelipeaux does not exist, and the boundary had to be negotiated anew.
Around the same time, the dramatically named Mountains of Kong appeared on maps of West Africa, apparently placed there originally by English cartographer James Rennell. It wasn’t until the 1880s that French explorer Louis Gustave Binger discovered that they don’t exist either. They persisted in Goode’s World Atlas until 1995.