64 Pa. Stat. § 470
It shall be the duty of the county surveyor of each county, to whom the surveyor general may send special lists of warrantee names of unpatented tracts or parts of tracts of land, and other data relating thereto, situate in the county for which such surveyor shall have been elected or appointed, to endeavor to ascertain the names and residences of the owners, agents or occupiers, and location of said tracts or parts of tracts, or any of them, and to give personal notice in writing to said owners, agents or occupiers, that said tracts or parts of tracts are unpatented, and that unless the arrearages shall have been paid within six months from the time of sending or serving said notice, the board of property may direct proceedings to be commenced by the attorney general to enforce payment under the provisions of the act to which this is a further supplement: Provided, That when unpatented lands as aforesaid are unoccupied, and the owners are non-residents of the county, and have no known agent or agents within the county, the said notice may be given by sending it by mail, addressed to the owners or agents, and directed to the post office nearest their place of residence or usual place of business: And provided further, That when lands as aforesaid are unseated, and have been sold for taxes, and the time limited for their redemption has not expired, it shall be the duty of the county surveyor to give notice, in the manner hereinbefore provided, to the purchasers or their agents, and also to the parties, or their agents, who last paid the taxes thereon previous to the sale.
64 P.S. § 470