For those who are searching in western Pennsylvania for their family roots, consider checking the Heinz History Center in Pittsburgh. The only known copy of a paper first written in 1931 by Schenkel which was taken from early court documents can be seen at the Heinz History Center.
Slavery was prohibited in Pennsylvania in 1780. However, the masters had to register their slaves by Nov 1780 or the slaves would be free. There were some other rules, but in general, the slaves would become servants until the age of 28. At that time, they would be freed.
In 2002, the Western PA Genealogical Society published the names of the negroes and mulattos which had been registered with the courts in Allegheny County from 1783-1813.
Ahhh, genealogy. Digging up the past one court document at a time can lead to some interesting discoveries. And, then there are the other questions raised......
Western Pa Genealogical Society Quarterly, Vol 29, No. 1, ppg 33-43.