List of U.S. Routes in Pennsylvania (English Wikipedia)

Bureau of Maintenance and Operations (January 2015). Roadway Management System Straight Line Diagrams (Report) (2015 ed.). Pennsylvania Department of Transportation. Retrieved June 30, 2015.
Bureau of Maintenance and Operations (January 2015). Roadway Management System Straight Line Diagrams (Report) (2015 ed.). Pennsylvania Department of Transportation. Retrieved June 30, 2015.

transportation.org

Special Committee on U.S. Route Numbering (November 2020). "2020 Annual (Fall) Meeting Report to the Council on Highways and Streets" (PDF) (Report). Washington, DC: American Association of State Highway and Transportation Officials. Archived from the original (PDF) on January 10, 2021. "USRN Applications" (PDF). Archived from the original (PDF) on January 10, 2021.

Special Committee on U.S. Route Numbering (November 2020). "2020 Annual (Fall) Meeting Report to the Council on Highways and Streets" (PDF) (Report). Washington, DC: American Association of State Highway and Transportation Officials. Archived from the original (PDF) on January 10, 2021. "USRN Applications" (PDF). Archived from the original (PDF) on January 10, 2021.
Special Committee on U.S. Route Numbering (May 14, 2015). "Special Committee on U.S. Route Numbering Spring 2015 Report to the Standing Committee on Highways" (PDF) (Report). Washington, DC: American Association of State Highway and Transportation Officials. Archived from the original (PDF) on June 3, 2019. Retrieved June 2, 2015.