I think you will really enjoy Cohen's book TJ. Like yourself, I was very aware of the folk scene in the region I grew up in the NYC region and was not familiar with all the other great pockets of folk interest.   Cohen does a nice job of covering some of these.

As you noted, the "revival" did begin during the earlier part of the 20th century, and could probably be traced even further to the collectors who predated the efforts. The term has been alligned with the commercial interest of the late 50's and early 60's, but the revival in folk heritage and song goes back further.

There is another good book about the scene in and around Boston and Cambridge during the 60's - "Baby Let Me Follow You Down".