I like the related places feature of the "old" Family History Library Card Catalog. That is the feature of the old catalog that allows me to see what a place is a part of and what places it contains. The new catalog does not do that--at least not yet.
Here's a link to the "related places" page for Knox County, Illinois.
Try it for your own locations. One should always be looking for possible records cataloged in regions larger or smaller than the one you thought to search for in the catalog.