File:Interstate Highway status unknown date.jpg - Wikimedia Commons
United States Numbered Highway System - Wikipedia
Office of Highway Policy Information - Policy | Federal Highway Administration
Infographic: U.S. Interstate Highways, as a Transit Map
This Simple Map of the Interstate Highway System Is Blowing People's Minds
Road Scholar: Fun Facts About the US Highway System - AutoSlash
9 Things You May Not Know About the U.S. Interstate Highways | From The Kitchen Cabinet
U.S. Route 100 | Intertropolis & Routeville Wiki | Fandom
United States Numbered Highway System | Intertropolis & Routeville Wiki | Fandom
The Math Inside the US Highway System – BetterExplained
FreightWaves Classics: Interstate 2 is a new addition to the system - FreightWaves
The Math Inside the US Highway System – BetterExplained
American Highways 101: Visual Guide to U.S. Road Sign Designs & Numbering Systems - 99% Invisible
American Highways 101: Visual Guide to U.S. Road Sign Designs & Numbering Systems - 99% Invisible
File:Interstate Highway status September 30, 1976.jpg - Wikimedia Commons
United States Numbered Highways
Fast Facts: The 47,000-Plus-Mile U.S. Interstate System | Feature | Car and Driver
File:Interstate Highway plan June 27, 1958.jpg - Wikimedia Commons
Renewing the National Commitment to the Interstate Highway System: A Foundation for the Future | The National Academies Press
Federal Highway System, United States
American Highways 101: Visual Guide to U.S. Road Sign Designs & Numbering Systems - 99% Invisible
Transportation History | American Interstate Highway System | GoVetted®
National Highway System (United States) - Wikipedia
