
Zip Codes Are Not Polygons (2001) - pizza
https://web.archive.org/web/20080723211144/http://www.manifold.net/cases/zip_codes/zip_codes.html
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pmiller2
Oh, man, this gave me some serious flashbacks to when I used to work with ZIP
code data on a regular basis. Besides the issues mentioned here, the following
are also true:

* ZIP codes can map to a single building: [https://convene.com/catalyst/buildings-new-york-city-own-zip...](https://convene.com/catalyst/buildings-new-york-city-own-zip-code/)

* Conversely, the largest ZIP code in the country (89049, coincidentally, also in Nevada) encompasses an area of about 10,000 square miles: [https://www.npr.org/sections/thetwo-way/2013/07/01/197623129...](https://www.npr.org/sections/thetwo-way/2013/07/01/197623129/the-zip-code-turns-50-today-here-are-9-that-stand-out)

* ZIP codes can map to more than one state or county: [https://gis.stackexchange.com/questions/53918/determining-wh...](https://gis.stackexchange.com/questions/53918/determining-which-us-zipcodes-map-to-more-than-one-state-or-more-than-one-city)

* ZIP codes can, and do change: [https://fas.org/sgp/crs/misc/RL33488.pdf](https://fas.org/sgp/crs/misc/RL33488.pdf)

As a result, ZIP codes are not the most useful method to use when referring to
a geographic area, unless, that is, you happen to be a USPS carrier attempting
to deliver a letter or package. Unfortunately, like Social Security numbers,
ZIP codes have been shoehorned into all sorts of places where they don't
really work ( _e.g._ statistical surveys, to give an idea where someone
lives).

It's a mess. My advice is that if you're looking to use ZIP codes for pretty
much anything besides mailing stuff, don't do it, unless you know what you're
doing. Even if you know what you're doing, think really, really hard before
using a ZIP code for something it's not actually intended for.

~~~
watersb
If we count ZIP+4 codes, my garage has its own ZIP code. It's a single car
garage (but platted on a distinct tract from the house). In a village in the
desert southwest, I guess they had extras numbers.

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JJMcJ
Sales tax, ZIP code crosses county line, one county has a sales tax surcharge,
the other doesn't.

Not ZIP precisely, but even the "City" causes problems. The address is the
name of the post office that delivers your mail, not the municipality where
the address is located.

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wodenokoto
Great little article. Straight to the point, easy to understand and with a
good message.

Kinda a shame that it is hidden away in an archive.

