Just because I can, yesterday I added a Wizard of Oz search engine to this site. You can hit that page and search all of the public domain Oz books by Frank Baum — and soon, all of Ruth Plumley Thomson’s Oz books that are in the public domain. It will return a list of any chapters where the search term appears, so, for example, you could find all of the places where Baum writes about Loonville.
The output is still a bit less helpful than I’d like, but I can fix that easily enough.