16 Pa. Stat. § 5851
Whenever different parts of any municipality or any part of such municipality and any municipality bordering thereon are separated therefrom by any intervening valley or ravine, and the county commissioners shall decide it necessary that a public bridge for the purpose of connecting the territories thus separated be constructed and that such bridge will be of substantial advantage and benefit to the taxable inhabitants of the municipality bordering thereon or municipalities adjacent thereto, such county may contract with such municipality for the laying out and construction by such municipality of such bridge and may pay to the municipality such portion of the cost thereof as the county commissioners shall deem reasonable, and shall appropriate money, levy taxes and incur indebtedness therefor.
16 P.S. § 5851