Lake Superior had many large islands in Robert Morden's 1698 map and John Senex' similar map of 1719. Even Guillaume de l'isle's map of 1718 showed an elevated plain.

Map of Savanna Portage Trail, 1956. Minnesota Conservation Department, Division of Forestry. A3/0V5, Drawer 7, Folder 8. State Parks Maps and Drawings, Minnesota Division of Parks and Recreation ...