53 Pa. Stat. § 16400
The streets, lanes and alleys within the said city of Philadelphia, heretofore opened for and dedicated to public use by private persons, and that all streets, lanes and alleys, which have been directed and laid out by the supreme executive council, for the accommodation of the purchasers of the public lots within the said city, that have been or shall be sold, so far as the same are laid out through the said public lots, for the redemption of the bills of credit of this commonwealth, dated the twenty-ninth day of April, 1780, shall be considered and deemed highways, according to the records thereof remaining in the surveyor-general's office, as fully to all intents and purposes, as any highways laid out by order of the court of quarter sessions of any county within this state.
53 P.S. § 16400