Embedded Files
100 years of US routes: 1926-2026
Endpoints of
Mileage: in 1989 AASHTO listed a figure of 108 miles for US 310. That is reasonably close to our own 2020 measurement, which yielded 103.6 miles. 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).
c. 1927, Rand McNally
US 310 has been around since the beginning in 1926 (the preceding image was from AASHO's April 1927 route log). Its purpose was to connect US 10 at Laurel with US 20 near Greybull. Today there is no US 10 west of Fargo ND, but its "child" US 310 still hearkens back to its existence through Montana. US 310 serves as an example of a north/south branch route which had to be assigned an east/west number (because it did not connect with any other north/south routes)...
...but interestingly, Wyoming signs US 310 as an east/west route anyway. Today US 20 west of Greybull is joined by US 14 and US 16, but the "east" terminus of US 310 remains the same -- these photos were looking west on US 14-16-20:
Elbert, Jul. 2005
Greybull
US 310 begins to the right; that former sign bridge has since been replaced with ground-mounted signs:
Sanderson, Sep. 2022
This next set of photos shows signage for traffic heading the opposite direction (east on US 14-16-20); the east beginning of US 310 is to the left:
Elbert, Jul. 2005
Sanderson, Sep. 2022
At the "east" end (or south end) of US 310, this next photo shows how the intersecting routes at the junction were signed:
Sanderson, Sep. 2022
The sign bridge visible in the distance is shown close-up in these next two photos:
Elbert, Jul. 2005
The stop sign in the distance marks the actual terminus of US 310, but there was no additional route signage ahead.
Sanderson, Sep. 2022
Heading to the north in 2022, there was no confirming marker, and in fact no references to US 310 at all until Lovell (a distance of 27 miles!) But here is a photo of one trailblazer heading that direction:
Winkler, Aug. 2000
Laurel
Heading into Montana from there, directional signage on US 310 changes from east-west to north-south. Today most signs indicate that the north end of US 310 is still at its junction with old US 10 (now Business I-90) in Laurel. This photo was looking north on US 310 and east on US 212, just south of the I-90 interchange:
Elbert, Jul. 2009
Those sign panels were replaced between 2011 and 2015, and the US 212 shield on the right was erroneously changed to a US 310 shield. So now, heading north on US 310, this signs implies that US 310 goes three different directions from this junction. It was still wrong as of 2024:
Google Maps Street View, Aug. 2024
In about 2013, the panels on that sign bridge were replaced, and instead of a US 212 shield on the right, there was an erroneous US 310 shield. But actually US 212 and US 310 split at that point: from there US 212 is overlapped with I-90 through Billings, all the way to the Little Bighorn Battlefield. US 310 continues north another mile or so, to its junction with Main Street, or Business I-90:
Hamilton, Jul. 2004
So today, although US 310 has been orphaned, its number still bears witness to the time when its parent, the once-grand US 10, ran through these parts. Heading east on Main, the signage looks like this:
Hamilton, Jul. 2004 (still there as of 2021)
It is unclear whether the "TO" banner was meant to apply only to I-90, or to US 310 as well. Heading the opposite direction, there was a US 310 sign posted as if Business I-90 is US 310...
Elbert, Jul. 2009
...but probably the intention was to have a left-arrow included there, because there is no mention of US 310 on the upcoming assembly:
Elbert, Jul. 2009 (replaced later that year; verbiage same as of 2021)
Sometime between 2009-2018 a crew replaced the highway signs in Laurel, and that "West 310" sign was simply replaced in-kind instead of being fixed:
Balaguy, 2020
Anyway, if a driver took that left turn ahead, they would not see the first confirming marker until south of I-90:
Sanderson, Mar. 2000
It seems US 310 is predominantly signed north-south in Montana, except for the "West 310" sign shown above, and except for some signage around the US 212 split at Rockvale.
Research and/or image credits: Nathan Balaguy; Chris Elbert; Alan Hamilton; Dale Sanderson; Michael Summa; Jonathan Winkler
Page originally created 2000;last updated Aug. 26, 2025.
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