[collinmanderson]

I agree using the preferred city name works just fine for USPS, though maybe not for UPS/Fedex.

What I want to know is: Why isn't this preferred city+state mapping dataset for zip codes publicly available from USPS? It would be like 40kb of data for the entire thing. Why is this not public domain from the US Government?

Edit: or is this what I'm looking for (the "Physical City", "Physical State" columns? https://postalpro.usps.com/ZIP_Locale_Detail

It's missing 00501 at least (which zippopotam has), and military zip codes (which zippopotam doesn't have). Military zip codes are included in this file: https://postalpro.usps.com/areadist_ZIP5

Also fun fact 88888 is for "Operation Santa" uspsoperationsanta.com, which zippopotam is missing, but appears in the areadist_ZIP5 file.

[jcrawfordor]

Unfortunately these USPS datasets are not public because USPS sells them. Or in some cases, the pattern tends to be that USPS has a contract with a provider (part of what I call the Postal Industrial Complex) that maintains the database and then sells it to both USPS and everyone else. Since these databases are used primarily by bulk mail services, they're fairly expensive and represent an important revenue source to USPS. Remember that USPS is semi-privatized, so they're looking for fees they can charge like everyone else... especially fees that can be changed more easily than postage rates.

That said, the ZIP DB is indeed not very large, so you can find copies of it. You won't generally find complete copies of the City State file but I wouldn't be surprised if there is one out there.

[8n4vidtmkvmk]

That's not nearly as good as Canada's H0H 0H0.

[mxdvl]

Which thankfully Zippopotamus supports: https://api.zippopotam.us/CA/H0H