Vantage Highway in Kittitas County and Pine-City Malden Road in Whitman County

[Amaury]

Does anyone know if these used to be part of a US highway or local state highway? I ask because both of these have mile markers on them, which, as far as I know, are only used on numbered routes, even on former ones, where they didn't see a need to remove them. Similar to something like Washington State Route 10, where the mile markers are still as if it were US Route 10, which, according to Wikipedia, still exists, it's just much, much shorter.

For context, Vantage Highway connects Kittitas and Vantage. Pine City-Malden Road starts at a junction with Washington State Route 23 and ends at a junction with Rosalia Road, just outside Rosalia town limits. It doesn't directly connect to US Route 195, but it leads to it.

[Bruce]

Vantage Highway was part of US 10. Don't think Pine City/Malden ever had a state highway.

There's a lot of county-maintained highways that have mile markers, so it's hardly unusual. A few examples in my area: Mountain Loop Highway, East Camano Drive, Kayak Point Road.

[Amaury]

Okay, so I was wrong. I was under the impression only numbered highways/routes had mile markers.

What was US Route 10's routing? I know it ended in Seattle and that a lot of it was replaced by Interstate 90 (the Lacey V. Murrow Memorial Bridge, which carries eastbound Interstate 90, used to carry US Route 10), but beyond that, I can't seem to find anything showing its former routing.

[KEK Inc.]

If you go to Frenchman Coulee (near the Gorge Amplitheater), there are historic US-10 markers.

Here's a highway map from 1931.  This is why you see 'Sunset Highway' in Issaquah and Cashmere, since US-10 used to route through Blewit Pass.
https://cdm16977.contentdm.oclc.org/digital/collection/p16977coll18/id/95

The Vantage Highway and the floating bridges were built in the 40s I believe, so this 1957 map shows a more modern routing.
https://cdm16977.contentdm.oclc.org/digital/collection/p16977coll18/id/83/

I'm sure during the late 50s, I-90 was starting to be constructed.

[Amaury]

Even with enlarging the maps, it's hard for me to tell what's what.

Something this or this, with the red line, would make it far easier, but sadly, I doubt there exists something like that for this route.

[Bruce]

Even with enlarging the maps, it's hard for me to tell what's what.

Something this or this, with the red line, would make it far easier, but sadly, I doubt there exists something like that for this route.

Cross-referencing with other maps makes it fairly clear. There's also resources like USGS TopoView and HistoricAerials that can overlay them onto modern maps.

I do plan on creating a KML map for US 10 in Washington eventually, but it'll take some time. I also have to decide which version(s) of US 10 to depict, as there have been some significant routing changes over its 40-ish years of existence.