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100 years of US routes: 1926-2026
Endpoints of
This page is about the south segment of US 191 (not to be confused with the separate north segment of US 191). Prior to 1981, US 191 was a single, continuous route. But in June of that year, a big change was approved for US 191: the route was extended south to Chambers AZ via what had been US 187 through Wyoming. In order to get there, US 191 was assumed to follow an implied route through Yellowstone National Park. However, since US routes do not exist in Yellowstone, this action created two separate, disconnected segments of US 191.
Our 2020 measurement yielded 1211.3 miles for the south segment of US 191. Want historic mileages? Our handy reference book includes the mileages that were published in all 13 of AASHO/AASHTO's historic route logs (spanning the years 1927 to 1989).
1926-1981
Originally US 191 was not a split route; see this page
1981-1992
North: Yellowstone, WY
South: Chambers, AZ
1992-present
North: Yellowstone, WY
South: Douglas, AZ
Linked pages.
Change sections with white color.
Update migration tracker.
The northern terminus of US 191's south segment has always been at the south entrance to Yellowstone.
Chambers
This photo shows the former south beginning of US 191[s], as seen from westbound I-40 at Chambers:
Sanderson, Mar. 2013
This shot shows modern signage at what was once the south end of US 191[s], at its interchange with I-40:
Sanderson, Mar. 2013
c. 1983, Rand McNally
That map illustrates why it did not make sense to have US 191 heading north from I-40, while just six miles to the east it was US 666 heading south from I-40. Plus, Arizona was probably eager to be done with chronic US 666 sign replacements due to frequent theft. So in 1992, US 191[s] was extended east from Chambers along I-40 to Sanders, and then south, replacing what had been US 666 all the way to Douglas... or at least close (photos and more info on the Douglas page).
Research and/or image credits: Dale Sanderson; Michael Summa
Page originally created 1999;last updated May 5, 2025.
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