- Pennsylvania's Decommissioned US Highways
- From Names to Numbers: The Origins of the U.S. Numbered Highway System - Federal Highway Administration
- Location Reference System - PennDOT
- Pennsylvania State Highway VideoLog - PennDOT
- Pennsylvania's New US Highways - US 981, US 156 and US 819? - Bruce Cridlebaugh
- Traffic Information Repository (TIRe) - PennDOT
- US Ends - Dale Sanderson