Yes, and it's a great idea. I know that people can make overlays for Google Earth, and I found one recent example for railroads and historic coal sites in NE PA.
This one guy did an incredible job, for example (you need to have Google Earth installed, and download the kmz file from the first post on this site):
http://bbs.keyhole.com/ubb/ubbthreads.p ... er=1110979
It would be great to have a set of these for the entire USA by decade, showing the abandonments, etc.
Plus also, I believe people can later add photo links along all the routes so that users can click on those.
Imagine if there were photos for each specific decade map.
I'm not sure if it's Google Maps or Google Earth or both, but I have seen where if you choose a certain option, there will be little picture links for the exact spots along the route.