Answer: The IRS

Every list has to start somewhere; area codes, country codes, zip codes, etc. No matter the list, somebody is parked at the lowest number. When it comes to zip codes, there’s no exception. While there isn’t a coveted 00001 zip code hiding out anywhere in the U.S. (if there was we’d hope it was for the mailroom at the White House), there is most definitely a lowest number in use.

Alas, the lowest zip code isn’t a single digit or in possession of the Supreme Court or other such group. The lowest in-use zip code is 00501 and it belongs to the IRS mail processing center located in Holtsville, New York. Conversely, the highest in-use zip code, 99950, belongs to the city of Ketchikan, Alaska.

There’s nothing particularly novel about 00501 aside from the fact that it is the lowest assigned zip code, so we’ll leave you with a parting gift. The easiest zip code to remember, 12345, belongs to the General Electric utility company in Schenectady, New York.