It was abandoned by the British in 1772, taken over by Virginians in 1774 and renamed Fort Dunmore. It was again abandoned when the new Fort Fayette was constructed in 1791-92. This newer fort was used by General Anthony Wayne during the Indian wars in the Northwest Territory. This map is a later colored edition of the 1757 map by Bellin, however the engraving is not identical. Delaware's separation from Pennsylvania was not shown on many colonial maps because both colonies had the same royal governor.
Longitude is west from Paris.
According to the OED, a perch is about 5.5 yards. This may be the only map of Pennsylvania with such a scale. This image comes from a reproduction of the original published in the Third Series of the Pennsylvania Archives 1894. The image is from the northwestern portion showing the Schuylkill River. The complete map shows Philadelphia and surrounding territory with an inset map of the city center and lists of the land owners and acreage owned.