16 Pa. Stat. § 5831
The county commissioners of any county may accept, take charge of and enter upon the records as a county bridge, any bridge over any stream or river running into or through any county, which bridge has been erected and constructed at the expense of private persons or by public subscriptions, and has been opened to free public travel, used by the public and become necessary and convenient for the use of the public, upon notice in writing of the persons who erected or caused the same to be erected, or by the subscribers to the original subscription on which the money was raised to erect the same, or the heirs or assigns of such persons or subscribers, or by a duly authorized board of trustees representing such persons or subscribers, of their desire to donate the said bridge to the county wherein the same is situated. Where such bridge crosses a stream forming the boundary line between two counties, the persons or their heirs or assigns, subscribers or trustees representing them, as aforesaid, shall give notice in writing to the county commissioners of each of said counties of their desire to donate such bridge to said counties jointly.
16 P.S. § 5831