I've been trying to build a ham related website. I'm looking for a list of call signs. Here's the trick: I need the URL to change based on the zip code. I want to be able to put the link on a page, have someone click on it and not have to do anything else. I have checked three resources: The ULS database, QRZ, and Radio QTH. The lists are there, but the URL does not change based on individual searches.
You can use radioreference.com, as in this example: https://www.radioreference.com/apps/ham/?action=search&zipcode=12345
If you are building a site that allows someone to put in a zip code to see the hams around them, it may prove more beneficial to allow them to see the hams that are within a certain mile radius of the zip code. I did this for a club that was offering licensing classes and wanted to send postcards to all of the hams of a particular license class within a specified radius.
If this interests you, take a look at a site like zipcodestogo. I programmatically entered the zip code and radius and then stripped out the zip code information from the returned page. I then used this to filter a SQL database of the ULS data that was downloaded weekly from the FCC site. The ULS download is well documented by the FCC. This is what QRZ uses for their U.S. call sign lookups.
You can also drive the addresses of your filtered results to place pins on Google Maps to get a nice view of the ham population in the selected area.