16 Pa. Stat. § 9873
For each and every of the books of records belonging to the several offices of the prothonotaries aforesaid there shall be made, prepared and kept, at least two indexes of the matters contained in such books, one of which said indexes shall, among other things, contain the names of plaintiffs, and the other the names of defendants so arranged as to afford an easy and ready reference to said matters. And there shall also, for each and every of the books belonging to the several offices of the recorders of deeds aforesaid in which deeds or mortgages may be recorded, be prepared and kept two indexes, one in which the names of grantors or mortgagors, and one in which the names of grantees or mortgagees, as the case may require, shall be so arranged as to afford an easy and ready reference to the matters in said last-mentioned books.
16 P.S. § 9873