US 280 and US 380 in Arizona as part of the early US Route System

[Max Rockatansky]

Something that has fascinated me about US Route 89 in Arizona is that it appears that really wasn't initially clear where it was going to end.  On most early drafts of the US Route System US 89 is shown to end in Flagstaff.  US 280 is shown to be aligned from US 66 in Ash Fork south to US 80 Phoenix and US 380 is shown to be aligned from US 80 in Tucson south to Nogales.  There is some evidence that Arizona wanted US 89 to at least reach Prescott from the outset as the new State Highway from US 280 in Prescott to Jerome was originally planned as AZ 89.  AZ 89 was planned to reach Flagstaff when the existing highways were built to State Highway standards which didn't occur until 1938.  It seems that the solution to get US 89 to Prescott was to consume US 280 which ultimately led to it being extended all the way to Nogales instead.  There appears to be no evidence that US 280 and US 380 were even field signed as they only appear on the Rand McNally Highway Map in 1927.  AZ 89 became AZ 79 which eventually did become US 89A in 1941.

https://www.gribblenation.org/2020/04/paper-highways-us-route-280-and-us.html