an early map of south-central pennsylvania was produced by john armstrong in 1755, and showed the proposed chain of forts to protect the western frontier (waddell and bomberger 1996, 18-19). darlington's 1882 map was copied from armstrong's map on file at the public record office in london. croghan was commissioned by the provincial governor to manage the establishment of this line of forts in 1755, and used his existing fort for the defensive location at aughwick.