It is not from a site, it's a GIS application. I just plotted the ZIP codes of NSXCA members against a basemap of ZIP code locations.
Which after some more investigation may explain the blob in the Death Valley area near the CA/NV border. The ZIP codes in very lightly populated areas are big. I was only plotting ZIP codes, not city/state or lat/long. I think it just plotted them on the extreme edge of the area they were from. I'll check further to make sure though.
Re: south florida... look closely, they are there, they are just all RIGHT along the coast so they are harder to see because of the black line that defines the coast. They also make a line as opposed to a blob because they stretch from Palm Beach to Miami instead of being clustered around one spot like Orlando.
For reference, there are nearly 1000 ZIP codes plotted on that map. Most cluster in certain population centers and make lines or blobs.