There are directories and there are directories! If you go to the _www.historicaldirectories.org_ (http://www.historicaldirectories.org) home page and click on History Notes on the left hand side of the page all will be revealed. There are pages of explanation there. Well worth spending a bit of time reading it all - it expanded my thinking and the knowledge I've gained has been incalcuable. For me, it's all about context. A few directories in their opening pages (Preface/Address/ or whatever) will tell you when and how the information was collected but you may have to look hard for that info. Hope this helps. Enjoy! Ruth