I came across a really good blog on the National Road by Christopher Bustapeck. It has photographs, maps, narrative text of the road from Baltimore to Cumberland, Maryland and then west to Vandalia, Illinois.
He is also an editor at the Historical Marker Database, another excellent site.
Check it out at http://nationalpike.blogspot.com .
I've already put it on my favorites.
Right Up There with the Lincoln and 66. --RoadDog