NM History: Route 666 - The Devil's Highway - The Roosevelt Review
U.S. Route 491 - Wikipedia
U.S. 666: "Beast of a Highway"? - General Highway History - Highway History - Federal Highway Administration
Route 666: Highway to Hell: Toepfer, J.D.: 9781737360308: Amazon.com: Books
New Mexico Route 666 – Sticker – Metal the Brand
Tour Test: Riding the Devil's Highway on a V-Strom 650XT | Rider Magazine
Pennsylvania Route 666 - Wikipedia
File:2019-08-06 10 34 34 View south along U.S. Route 15 and U.S. Route 29 (James Madison Highway) at the exit for Virginia State Route 666 (Culpeper) in Braggs Corner, Culpeper County, Virginia.jpg - Wikimedia Commons