We use Site Codes to keep track of which meetups are in which areas. Site Codes are your closest 3 character airport IATA code - guaranteed to be a unique local reference.
The site codes are useful for us to figure out what is getting shipped where. They're also used to name the slack channels for local chapters (e.g. #_sea for Seattle or #_lga for Manhattan). Slack channels for local chapters will soon be replaced by City Pages.