Washington State Route 504 - Spirit Lake Memorial Highway

[Amaury]

So, what is now Washington State Route 504 Spur used to be part of the old highway 504 that was destroyed in the Mount St. Helens eruption in 1980. Now it just leads to a dead-end at a WSDOT maintenance facility. When most of the highway was rebuilt, it was relocated farther north, according to Wikipedia: https://en.wikipedia.org/wiki/Washington_State_Route_504

In that same article, I've seen a couple photos of the damage, one with a buried road sign. My question is, are there any photos or videos showing what the old highway 504 looked like prior to the eruption? I haven't been able to find any. I've been to the Johnston Ridge Observatory a couple times now, of course via current SR 504, but I'm curious to know what the old highway was like, such as its routing, curves, etc.

[Mapmikey]

Suggest historicaerials.com which shows Topo maps of the original routing.  There are 1951 aerials but don't cover very far east of the WA 504 Spur area.  Also 1981 aerials which doesn't help your question much as most of the old road was buried but does show the immediate aftermath.

Another potential source for questions like these is vintageaerial.com where you can sometimes see photos that include the road itself and county maps sometimes back as far as the late 1960s.  Cowlitz/Skamania Counties are not in their dataset, however.

Lastly, the National Archives has county maps of nearly everywhere for a late 1930s date and a late 1940s date
https://catalog.archives.gov/search?q=skamania%20county%20washington%201950&f.materialsType=mapsandcharts

Through these county maps you can see that there was already a former alignment for parts of WA 1-R by 1950 with the newer alignment being eventually buried in 1980. 

These last two solutions would also show you the former alignment of US 2 (or former US 10A) in the Wenatchee area.

Repository for Washington state highway maps is here: https://cdm16977.contentdm.oclc.org/digital/collection/p16977coll18/search/page/1

[xonhulu]

This doesn't show much of the old road, but if you want to see what the area around Mt St Helens looked like pre-eruption:

https://www.youtube.com/watch?v=qKN4PsJiTk4

The pre-eruption photos start around the 4:00 mark.

I grew up in the Longview area, and my family went up there many times.  I just remember the upper section of the old Toutle River Hwy as being a pretty typical mountain road along a river canyon; the closest analog I can think of is US 20 east of Cascadia down here in Oregon.

I remember the impressive old-growth forests around Spirit Lake much more clearly, as well as the spur road south to the flanks of the mountain.  I did climb part of the way to the summit one time, turning around at a formation called Goat Rocks.  Regrettably, I was only 15 when the mountain erupted in May, 1980, so all those family trips were when I was a young kid, and I'm afraid my recollections aren't the clearest.

[JasonOfORoads]

Another solution I've found is to download the KML versions of the USGS topographic maps from their website and loading them into Google Earth. That's helped me find a ton of old alignments of Oregon highways, and I can only imagine it would work here presuming they had data in all areas prior to 1980.

[xonhulu]

Here's another video I found.  It shows a little more of the Spirit Lake area development. 

https://www.youtube.com/watch?v=DxK6P2TRmX8

It does have a few shots of the old highway but nothing really definitive.  They're mostly showing the pre-eruption Red Zone roadblocks. But it has a good recap of the events leading up to the eruption. 

There's also a great shot looking south over Spirit Lake that shows the highway spur to Timberline heading south through the forest; you can see it in the video's thumbnail.  I think it might also show the road's terminus up on the mountain's flank below the Goat Rocks.