I've been fascinated with old roads for quite a few years. Maine has a lot of them; somewhere along the way DOT decided the original road needed to be straightened, but there were already houses on it, so they left it behind and built the new line around it. Some are easy to find ("Old County Road" sits to the right of "County Road") and some you need to look for other clues, like a bunch of houses that look like they were built facing backwards. When I find one and figure it out, it just makes me happy.
Yesterday we visited my parents and my brother, and I think I identified the source of this fascination. When we moved to town in 1978, they were in the process of changing the road. I don't remember it specifically, but there was the side road, just beyond the turnpike, that runs about a half a mile and dead ends each way, with a huge old farm at one end that is obviously facing the wrong way. I remember asking my mom about it, and suddenly, I could see where the road used to come in front of the remaining houses. I could see the path the old bridge took and how those yards on the other side were affected by the change. And I've been looking for them ever since.
(And yes, I did find old 173 SUD as we were driving home from Quebec City...)