Try 89183 which is a new zip in Las Vegas. I used Google Earth to see exactly where the coordinates where it was telling me. They were about 10 miles off from where mapquest locates it to be.

I have searched many sites, and most give me the same coordinates as ziplist. The only ones who have gotten it right so far are the mapping websites (mapquest, maps.yahoo, etc) and http://www.xionetic.com, but theirs isn’t a database but instead a software package.

After many hours of research, I found this blog and thought I would let you know not to completely trust the mentioned db, before continuing my search for a truly correct list.

That is absolute genius on your part. Since there are 5000-something changes to the zip code data every year, it won’t solve the “keep the data updated” problem but it is certainly good enough for 90% of the applications out there.

Well, unless you hit the web service each time you want to do the lookup. No local storage == data stays updated. However, there may be implications for your app in terms of response time if the ‘net or the service is slow. There is also the issue of rate limits (1/sec/ip address for google, 5000/day/ip for yahoo), but since both use IP address as a key, you can circumvent the limit by assigning more than one IP per server and round-robin which one you use to make the request.

@Duncan – I had never considered using Google or Yahoo’s geocoding service to reverse engineer the postal code data. That is absolute genius on your part. Since there are 5000-something changes to the zip code data every year, it won’t solve the “keep the data updated” problem but it is certainly good enough for 90% of the applications out there.

DW