[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.