Posts Tagged ‘ZIP code’

Unique Zip Codes – What Are They?

If you have ever run into a unique ZIP code while doing address lookups or validation, then there is a good chance that they may have caused some confusing results for you. Take the following address as an example:

123 Not a Real Street
Schenectady NY, 12345

To most users, this address looks like it is fake. But if you send it to an address checker like DOTS Address Validation – US, to be validated and standardized, then you will get a response like the following.

Our service indicates that this is a valid mailing address. So what gives? This might lead one to believe that something went wrong in the address checker or validation engine. But there is a perfectly reasonable explanation for cases like this. If we take a look at the DPV Notes returned by our service, we will see Code 3, which indicates that the ZIP code provided is a unique ZIP code.

What are unique ZIP codes?

In short, unique ZIP codes are high volume mail receivers that receive mail at one location and then distribute the mail internally. Unique ZIP codes generally are used by large organizations, government buildings, universities or large medical facilities. For these cases, the USPS would drop off all the mail at one single location, and then the mail recipients would distribute it to the necessary parties internally. Since all that mail is distributed internally, the USPS and our services by extension will mark every address with a unique ZIP code as valid and deliverable.

How should we handle unique ZIP codes?

Great question! These are cases that would certainly require some type of additional logic to process. If you have a user submitted form, perhaps you could process this by asking the user to double check the postal code entered. This could help ensure that the unique ZIP code was not entered by mistake.

If you are cleaning up a database and find a number of unique ZIP codes in your data, this might be a case where you would want to contact the owner or operating organization of the ZIP code to ensure that the addresses obtained are valid.

Each use case is different. If you want some assistance or suggestions on how to best handle unique ZIP codes for your case, reach out to us at We’re always happy to make recommendations and help customers get the most out of their data.


Understanding unique ZIP codes before you encounter them can be key to preventing any hiccups that may occur when using Address Validation – US and address checking in a production environment. Preparation and knowing different scenarios like this are key.

We strongly recommend reviewing our developer’s guide and all the possible DPV Note codes that the service can return. If you have any questions, don’t hesitate to ask us; we’re always ready to help educate our customers to be their own data experts.

In case you were wondering, the ZIP code 12345 belongs to the world headquarters for General Electric.

Fun Facts About ZIP Codes

Addresses in the United States used to be a simple matter of a street location, a city and state, and perhaps a city-specific postal zone. But by the 1960s, between massive increases in mail volume and the advent of computerized scanning and sorting equipment, the U.S. Postal Service needed a strategy to automate and speed up delivery. The result was the Zone Improvement Plan, or ZIP code for short, and it has since become a model for the world’s postal codes.

At Service Objects we make part of our living resolving and geolocating addresses, including their ZIP codes, so we thought you might enjoy discovering some of the history – and idiosyncrasies – behind those numbers at the end of your mailing addresses.

A ZIP Code Entertainment Spectacular

When ZIP codes were first introduced in 1963, their use wasn’t mandatory. (And believe it or not, still isn’t.) So to help convince people to switch from their old address formats, the U.S. Postal Service commissioned a 15-minute long educational film led by musical group The Swingin’ Six. It featured music, comedy, and even romance, juxtaposed with a leaden-faced appearance from the Postmaster General of the United States.

Here it is, preserved for posterity on YouTube. As a disclaimer, we take no responsibility if you can’t get their songs out of your head.

In keeping with a tradition of using cartoon characters to raise social awareness (think, for example, Popeye getting children to eat their spinach), the Post Office also commissioned an artist to create their new mascot: Mr. ZIP. In character form, he signified a new generation of speed and accuracy.

Can a Person Have Their Own ZIP Code?

The answer is yes – but only if you are the President of the United States or the First Lady. The POTUS’s ZIP+4 code is 20500-0001, while the FLOTUS is 20500-0002. Both are subsets of the White House’s dedicated ZIP code of 20500, which also has +4 codes for its postal station and Greetings Office. (You can actually look these up on the USPS ZIP code search page for 1600 Pennsylvania Avenue in Washington D.C.).

The one other example of an individual with their own ZIP code happens to be U.S. Forest Service mascot Smokey Bear. Between his popularity as an advertising icon and interest in the real live Smokey (an orphaned bear cub rescued from a 1950 forest fire) at the National Zoo in Washington D.C., he received so much mail that he was granted his own ZIP code of 20252. Although this ZIP code was eventually decommissioned in 1993, it was recently brought back by popular demand, as he still gets letters from children across the US.

Further up North, one other individual sharing this honor is Santa Claus, who fittingly has the Canadian postal code of H0H 0H0. No such luck in the US however, where letters to Santa go to the actual town of North Pole, Alaska and its ZIP code of 99705.

The ZIP Code That Got Swallowed Up

Somewhere in central Pennsylvania – off I-80, nestled between the Pilot Travel Center and the local Walmart – is the little town of Conyngham, PA. Better known as the town that was swallowed up by another ZIP code. You see, Conyngham and its roughly 2000 residents, with a ZIP code of 18219, is completely surrounded by the Sugarloaf, PA ZIP code of 18249, as shown in the image below.

(Image courtesy Google Maps)

In fairness, Sugarloaf’s ZIP code is further divided by ZIP+4 codes into four separate regions within the 18249 ZIP code. But poor Conyngham is still surrounded. And some poor homeowner is probably trying to explain to an insurance agent that even though she lives WITHIN the 18249 ZIP code, she doesn’t live IN it.

This situation can also occur at a street level, which is in fact surprisingly common: a street-assigned ZIP code may extend into an area where this street is surrounded by a different ZIP code. So a different ZIP code may be as close as your backyard neighbor!

Situations like these may sound humorous, but as this article points out, they can have a real impact on people’s lives. Issues such as insurance rates, voter registration, and jury duty can be affected, as well as more serious concerns such as emergency response – not to mention a possible loss of status and property value when your home is in one neighborhood but your ZIP code is in another. In response to these concerns, the USPS now has a mechanism for reviewing ZIP codes on a case-by-case basis.

Those Numbers Actually Mean Something

ZIP codes aren’t just assigned at random: each digit has a specific function. The first digit, from 0 to 9, places a mailing destination in one of ten broad mailing regions of the United States. The next two digits narrow down this destination to a central Post Office for a smaller region such as a city. Finally, the last two digits defines the destination further to a local Post Office.

So-called ZIP+4 codes refine the destination further, with the last four digits signifying data ranging from a PO Box number to a floor within a building.

Some entities are so large or specialized that they have their own ZIP code, including the Empire State Building, Dodger Stadium, the CIA, and New York’s LaGuardia Airport.

Putting More ZIP in Your Contact Data

As you have probably learned from this article, determining ZIP codes and their corresponding locations isn’t for the faint of heart. But fear not, we can help. Our DOTS Address Validation – US service helps correct and complete US addresses down to the ZIP code level, and our DOTS Address Geocode service provides accurate latitude and longitude coordinates for geographically-based applications ranging from insurance rates to home values. Contact us anytime, and we’ll respond faster than Mr. ZIP!