The list of Zip Codes in LegalServer is used by the Address blocks to automatically insert the neighborhood, city, county, and state when a user enters a zip code. Whether neighborhood and county are inserted depends on the configuration of the Address block.
Administrators maintain zip codes in on the Admin > Zip Codes page.
Click a zip code to see it's current settings. Click the Edit pencil or link to see and modify the neighborhood, city, county, and state, associated with a zip code. Click the Create New Zip Code link in the side menu to add a new zip code.
Multiple Cities for one Zip Code
A zip code can cover more than one city, so the edit page for each zip code allows you to select multiple cities. (Cities are maintained in Admin > Lookups)
A user entering a zip code with multiple cities will see the popup window stay open, waiting for them to choose one of the values. The city and state will not autofill unless they click one of those values. Organizations often choose to only associate a zip code with the single default city (per usps.com) so intake workers aren't slowed down by having to choose in the popup.
If multiple counties are selected for a zip code, then the popup window will show an entry for each city - county combination.