First let me recommend "Bound Away - Virginia and the Westward Movement" by David Hackett Fischer and James C. Kelly  of the Virginia Historical Society.
(University Press of Virginia, 2000) which has several illustrations and authoritative discussions of emigration into Virginia, migration within Virginia and migration out of Virginia.

It you can visit Richmond, the Library of Virginia's Map Room, request these maps which show immigration routes like the one you mentioned: 
730 / H6 / 1933 and 755/ H6 / 1921.

Or Google "map of migration routes in  Virginia", this will yield several links like this one:

http://freepages.genealogy.rootsweb.ancestry.com/~tqpeiffer/Documents/Ancestral%20Migration%20Archives/Migration%20Webpage%20Folder/Routes%20to%20VA,%20NC,%20SC,%20GA.htm  


William Milam
www.milaminvirginia.com 

To subscribe, change options, or unsubscribe, please see the instructions at
http://listlva.lib.va.us/archives/va-roots.html