I discovered a new resource for researching prototypes and thought I'd pass it on - the USGS's
EarthExplorer site.
I've been looking for OE/SP&S track schematics and ROW photos from the early BN era because a lot has changed in western Oregon since the 70s. The BN and SP ended up abandoning parts of the respective lines and sharing trackage and the lines became even more homogenized with the P&W/W&P takeover of BN and SP tracks in the 80s; plus a lot of urban development has occurred in terms of the industries along the lines - buildings torn down, industries expanded, etc. So field research, using contemporary tools like Google Earth, etc. has been hit or miss. The EarthExplorer site offers old Federal gov't aerial imagery, a lot of it high res, and I was able to find images dating back to that time period to help my research. I found aerial imagery from 1974, which helps me discern what structures still exist and identify new architecture and infrastructure that I should exclude from my layout planning.
Check it out.