I came across this website and found it very beneficial to the study of Thamnophis ranges. Watching the YouTube video was a big help before I went to the website. Here is a screen shot of the search I did on Thamnophis radix (imagine that).
With the wide variety of animal interests on this forum it will probably become bookmarks on many computers.
I believe this is a work in progress so changes will probably occur.
Finalish.mp4 - YouTube
Map of Life