The following section of county road in the county of Allegheny is hereby adopted as a State highway:
Commencing at a point in Penn Avenue, being State highway route number 120, in the borough of Wilkinsburg, Allegheny County, and running thence in a northeasterly direction over Swissvale Avenue, Park and Montier Streets, to an intersection with State highway route 228, north of the borough of Wilkinsburg, shall be adopted by the Commonwealth as a State highway, and shall be constructed, improved and maintained at the expense of the Commonwealth, under existing laws.
36 P.S. § 1742a