Source: Editions of Moll's Atlas Minor, 1729-, in Thomas Salmon's Modern History, and possibly others.
This is the "Post Road" map, which appeared in many editions of Moll's atlases and in the 1739 and 1744 editions of the Modern History, with many changes to the plate.
"An account of ye Post of ye continent of Nth. America as they were Regulated by ye Postmasters Genl. of ye Post House."
All postal stops and routes are listed on the lower right corner.