[Tangurena2]

As a rule of thumb, sure, you can presume that zip codes follow political boundaries (city, county or state). The vast majority of times, that's the case.

However, if you do a lot of mailing, you'll discover some zip codes that cross state lines (because some remote area is actually served by a post office across the state line).

Or some area where several towns & cities map to a single "preferred" name that the USPS uses (example: Centennial, CO).

Zip codes are for the convenience of USPS and to make their life easier. The edge cases are very fuzzy & fractal.