One of my favorite ideas that came up in the abecedary was cartographic vandalism: when a cartographer intentionally puts an error on a map. A famous example of this is the non-existant Mount Richard, near Boulder, Colorado; the mountain is generally attributed to cartographer Richard Ciacci.
But my favorite instance of cartographic vandalism surrounds two islands in Lake Superior. These islands – Isle Pontchartrain and Isle Philippaux – were of some strategic importance, and their ownership was debated at the Treat of Paris in 1783. Eventually, the decision was made that the border between the US and the British Colonies would put Isle Pontchartrain and Ilse Philippaux on US territory.
However, nearly a half century later when surveyors went to the region, they could find no trace of the islands, and eventually had to conclude that these islands didn’t exist. Such errors aren’t all that uncommon, except that the islands’ names suggest that this was no accident: French explorers named the islands after Louis Phelypeaux, comte de Pontchartrain, who was the government minister responsible for their funding. Possibly this was a late addition to a map, inserted to attempt to gain favour or more funding.