UPDATE! Jan 2016 I have made the main map default to terrain so you can see how the early routes followed the land. You can click on Map and change to regular view or over to satellite view to see what the area looks like. Maps are now managed through Google Maps API which gives a lot more flexibility.
Jan 2015; the lines have all been reworked and moved to line up on the roads much closer. Much easier to follow them through cities now. Many thanks to BrokenLug on the Delorme forums for figuring out how to edit and convert the files.
Color codes for the roads;
Red = oldest alignments. 20's - 30's
Brown = 30's - 40's
Green = 40's - 50's
Blue = Later non Interstate
Black = Not part of 66 but used to connect broken segments.
These dates are approximate because Route 66 was continually being moved, re-routed, improved and changed.