Per a conversation at lunch, it seems that 01001 is the lowest numerical ZIP code. It’s Agawam, MA, near Springfield in Hampden county. For more info on the zone improvement plan, see Wikipedia, the free encyclopedia.
Realm of the Wombat
Talking to myself since 1997
Nice work. I love learning.
Ketchikan has the highest ZIP code assigned by the United States Postal Service: 99950. ZIP Code 99999 is not reserved anywhere.
As I was searching for the lowest ZIP code value, I found 00501 is a “Unique” zip code (meaning it’s used for a specific company or organization) used for the IRS Service Center in Holtsville, NY. You can check it by going to http://zip4.usps.com/zip4/citytown_zip.jsp
and entering 00501. There may be other lower ones, but nothing lower that I’ve tried has worked.