Given that there are few truly national supermarket chains, I figured Costco would be a good place to use as a sample to show how national chains cater to local clientele.
For example, in the greater Miami area, Costco stocks the following products which may or may not be particular to the area but seem like they'd be unique to here:
Kirby black beans
Del Monte hearts of palm
Costco-made Guava cheescake
I'm curious to see what Costco stocks in other parts of the country that are specific to that region.