Congrats to NE2 (again, again) for winning the March 20 trivia night! Of course, that means he hosts next time. In the meantime, come chat with us!
Your link to the detailed highway history of Oregon doesn't work, though. Here's the correct link:http://egov.oregon.gov/ODOT/HWY/GEOMETRONICS/ROW_Eng/HistoryHighwaysOregon/HSHO.pdf
Here's Iowa: http://www.iowadot.gov/maps//msp/historical/transmaps.htm
The Virginia link seems to have died. Anyone have a new link?
I don't know if there's anything useful here that's not on the other maps, but Oklahoma also has traffic count maps going back to 1937: http://www.okladot.state.ok.us/aadtcnt/Default.aspx?list=staticMaps