Congrats to corco, who won our last trivia on July 15! Stay tuned for our next edition.
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