European knowledge of the interior of northern New England was sparse before the French and Indian War (1756-63). This can be seen in the representation of Moosehead Lake. The map was nonetheless the most comprehensive image available in the 1780s and so was used by the negotiators in Paris in 1782-83 to define the boundaries of the United States.
Note: This map is actually a separate display that runs concurrently with the larger exhibition. Following its link will connect you to a different website devoted to the map!