Old maps can reveal some interesting things.
I've been looking at the "Illinois Highway Maps" collection on the Illinois Digital Archives website, partly out of curiosity and partly in an attempt to get a better understanding of what early highways were in my native state.
The map in this blog post is from 1922. One of the first things I noticed was that the highways had no numbers. As one who has always heard highways referred to by their numbers (with the exception of highways referred as going "east of town," "west of town," etc.) the lack of numbers seemed confusing to me.
And so there were names. I was somewhat surprised to see "Swastika Trail" listed as one of the highways, particularly as it was one I've driven on numerous times in the past twenty or so years. Of course seeing the use of the word "Swastika" in a different context brought to mind another history lesson: how we interpret words changes over time.
I've never heard the highway referred to by this name--now it's highway 17. I'm not certain I've heard the other names used either. Old maps such as this one may provide names of routes or trails not documented elsewhere--remember old maps aren't usually part of full-text digital collections that can be searched the way print materials can.
If you've got Illinois ancestors during the time of the automobile, consider looking at the "Illinois Highway Map" collection. Or search for maps for your own state of interest.
You may be surprised at the things you learn in the process.