32 Pa. Stat. § 172
Except as hereinafter provided, no such lands shall be held and retained as county forests, or be transferred to the State as State forests by the county, against which there are any liens of record which have not been discharged by the county treasurer's sale or by failure to redeem the same. In case the county commissioners desire to retain and hold such lands as county forests or to convey them to the State as State forests, they may, after holding such lands for a period of two years after the county treasurer's sale, advertise such lands separately for sale in the manner provided by law for the advertisement of sales for taxes by county commissioners. A notice of the place and time of such sale shall be served on the owner of such lands and on any lien creditor, if known, and, if their whereabouts are unknown, then such notices shall be sent by registered mail, addressed to the last known post office address of the owner and lien creditor, and a return of the card showing receipt of such letter, or the return of the letter itself showing a refusal to accept delivery or a failure to deliver, shall be deemed sufficient service.
32 P.S. § 172