Ohio Byways and Byways
From a friend - I just found out about this myself.
When you go to the ohiobyways site, move the rectangle around on the Ohio state map to see routes on different parts of the state. There's a buncha stuff there....
This one has byways across the USA, organized by state. You choose a state on the menu on the RH side of the page, and get a map marked with the various byways in that state. Click on the byway, and you get detailed info on selected route and its history.