Zipcodes in the United States are postal routes, which aren't really polygons like cities. We can make an approximation, but that's not how they're defined. In

Zipcodes in the United States are postal routes, which aren't really polygons like cities. We can make an approximation, but that's not how they're defined. In some countries, point postcodes are common. We just spent a bunch of time on postcodes in Great Britain, which commonly only have a few addresses in each one. Even in the Unites States, some universities or other large institutions will have a "postcode" which is a single address. The US military also assigns postcodes to ships, which tend to move a bit more than your average building.