End of US highway 12
|Approx. time period||East terminus||West terminus|
|1926-1939||Detroit, MI (Cadillac Square)||Miles City, MT|
|1939-1959||Detroit, MI (Cadillac Square)||Northeast entrance Yellowstone National Park, WY|
|1959-1962||Detroit, MI (Woodward @ Jefferson)||Missoula, MT|
|1962-1967||Detroit, MI (Cadillac Square)||Lewiston, ID|
|1967-1970s||Detroit, MI (Cadillac Square)||Aberdeen, WA|
|1970s-2000||Detroit, MI (Woodward @ Jefferson)||Aberdeen, WA|
|2000-2005||Detroit, MI (Michigan @ Griswold)||Aberdeen, WA|
|2005-present||Detroit, MI (Michigan @ Cass)||Aberdeen, WA|
The east end of US 12 has always been in Detroit (although, as you can see from the table above, its exact endpoint has shifted around a bit over the years); you can view photos from there on this page.
US 12 didn't always make it to the Pacific Coast. The west end was originally at US 10 in Miles City MT. The photo below was taken from what was most likely its endpoint:
Elbert, July 2005
That's looking west on US 12/Business I-94. Despite the signage here, both designations continue to the left on Valley Drive. That used to be US 10, so US 12 probably would've ended at this junction. Below we're looking northeast on Valley Dr/historic US 10:
Elbert, July 2005
Eastbound US 10 continued ahead, and eastbound US 12 began to the right. Today that road has access to I-94 at exit 141.
In 1939, the US 12 designation was extended to Silver Gate MT, at the northeast entrance to Yellowstone National Park (you can view photos on this page). From Forsyth MT, it was co-signed with US 10 (roughly along today's I-90), through Billings. At Laurel, US 12 split off to follow the route which today is designated US 212: through Red Lodge, over Beartooth Pass, through Silver Gate, into Yellowstone. That was the case until 1959. That year, US 12 broke off from US 10 at Forsyth to follow its present route through Helena; it ended in Missoula at US 93, which at the time came in from the south on Higgins Avenue and left town via Broadway. The photo below is looking west on Broadway:
Field/Kalina/Nitzman, Sep. 2006
Today that's westbound Business 12 / Business I-90, and the two routes separate here. Historically, northbound US 93 was ahead, and southbound was to the left on Higgins, so US 12 came west to this point and ended here. Then, in 1963, US 12 was extended west again: this time over Lolo Pass into Idaho, roughly along Lewis and Clark's historic trail, to Lewiston. Where it ended, US 410 began (see my Lewiston highways page for that particular terminus). But this situation lasted only four years: US 410 was decommissioned in 1967, and the US 12 designation was extended west for the last time - mostly along 410's former route to Aberdeen, except for the segment between Naches and Elma WA. You can view photos from Aberdeen on this page.