Isle Philippeaux: The Phantom Island

Isle Philippeaux of Lake Superior was an official landmark to mark the border between the United States and what is now Canada.
In 1820, surveyors set out on a mission to stake out the international boundary from the Lake of the Woods to Lake Superior. These surveyors relied heavily on the information gathered by previous explorers of the area. It’s possible the maps they carried to guide them were updated versions of the Mitchell map.
“Thence through Lake Superior Northward of the Isles Royal & Philippeaux to the Long Lake” are the directions written in the Treaty of Paris.
After days and weeks go by, it became clear that those directions were worthless. Isle Philippeaux was not there. As they searched the freezing waters in vain, the surveyors slowly began to understand. Ilse Philippeaux was not there. It had never been. It was simply a phantom.

[@1SemperDad]

I believe it was common practice for cartographers to include "false landmarks" in an effort to detect map counterfeiters. These "false landmarks" were known only to the original creator and when they appeared on other peoples maps it indicated that the original was used to plagiarize the new map. Safe travels to Camden

[@SamsonHistorical]

That is sometimes the case. Usually is is a town or something small that doesn't change the topography. So basically their map is geographically accurate except for a word here or there. This level of falsity is extreme. Thank you!