DL has a handul of mini-hubs or to adopt the TWA lingo "focus cities." LAS is a very good example; LAX, BOS, MCO, PDX and even LGA are others.
However, back to your example, obviously, when you plug in two hubs of a given airline, there are going to be endless possible connections; I mean think how many cities DL flies to from both ATL and SLC. You could theoretically make in all of them. Not too practical given the amount of nonstops between them. UNLESS of course you're after segments for Medallion status or extra miles!!