The Counties of Western Pennsylvania merged, split up, and changed over time.
Below are a graphic examples of where county lines were and how William Locke's county of record would have changed with time.
To truly understand where William Locke lived and the changing names of the Counties he lived in, this website and booklet are helpful.It shows the changing boundaries of the various counties in Western Pennsylvania.
http://publications.newberry.org/ahcbp/downloads/states.html
Other County History resources include:
http://dgmweb.net/Ancillary/Geog/PA/PA-Cos.html
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http://www.rootsweb.ancestry.com/~pamercer/PA/PL/Maps/township_names.htm
Compiled and contributed by John MacDonald
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http://www.rootsweb.ancestry.com/~pamercer/PA/PL/ts/townships.htm
Follow Mercer County's townships as they evolve from the original six townships, through the division of Lawrence County and into the townships of today.
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Current Pennsylvania Counties.