Postal Zones Came Before Zip Codes

We found the reason the "ZIP" in "ZIP code" stands for "zone improvement plan."

Mignon Fogarty
2-minute read
Episode #773
The Quick And Dirty

ZIP codes were introduced in 1963, but they came from more rudimentary codes, called postal zones, that were first implemented in 1943.

Last week, we talked about how to write ZIP codes, and I included some history, mentioning that they were first introduced in the United States in 1963, which is true; but two people wrote in to tell me about earlier codes, called postal zones, that were introduced in 1943.

Barbara Hughes from Vancouver, Washington, gave this example from her childhood: 

“Prior to ZIP codes, the postal [zone] for East Cleveland was '12,' [and] we wrote our address like this: East Cleveland, 12, Ohio. The neighboring town was Cleveland Heights, and that address was: Cleveland Heights, 21, Ohio. I presume that … [these] 'evolved' into ZIP codes … Addresses were written as CITY, POSTAL CODE, STATE.

When ZIP codes were introduced . . . the numbers designated a large area to a progressively more focused, local area. Northeastern Ohio was designated as '441.' So therefore, the ZIP codes for East Cleveland and Cleveland Heights became 44112 and 44121, respectively. The ZIP codes inherited the existing postal [zone] system already in place. Not only that, addresses were now supposed to be written as CITY, STATE / ZIP CODE. The ZIP code was supposed to be the very last item in an address, not sandwiched between the city and state.”

Sue Hatfield-Green wrote in with a similar story about Dellwood, Missouri. She said its postal zone was 36, and it would be written as Dellwood 36, Missouri, and then after the introduction of ZIP codes, it became 63136, and the code moved from the middle of the address to the end.

If you’re wondering why postal zones were introduced in the first place in 1943, the Smithsonian National Postal Museum says it was because of World War II. Not only were people sending more mail, but the post office was hiring a lot of new and inexperienced workers to replace those who had gone to fight the war, and the numerical city codes made it easier for all those new people to keep up and sort the mail quickly. 

The postal zones weren’t everywhere, but they were widespread and were adopted without much resistance (I suppose because everyone wanted to support the war effort in whatever way they could). 

The postal zones weren’t as widespread as ZIP codes are today. The Smithsonian says postal zones were only used in 124 of the country’s largest urban areas. 

And since the ZIP codes did evolve from the postal zones, I think that explains why ZIP stands for “Zone Improvement Plan.” The two-digit postal zone number specified a small region, like a town, but with the new five-digit ZIP code, the sorter could start with the first number, which represents a group of states, go to the second two numbers, which represent a smaller area in that region, and THEN go to the small region like the town. The new number was an improvement on the postal zone or a zone improvement plan: a ZIP code.

Thank you for Sue and Barbara for sending me that interesting additional information!

Image courtesy of Shutterstock.

About the Author

Mignon Fogarty

Mignon Fogarty is the founder of Quick and Dirty Tips and the author of seven books on language, including the New York Times bestseller "Grammar Girl's Quick and Dirty Tips for Better Writing." She is an inductee in the Podcasting Hall of Fame, and the show is a five-time winner of Best Education Podcast in the Podcast Awards. She has appeared as a guest expert on the Oprah Winfrey Show and the Today Show. Her popular LinkedIn Learning courses help people write better to communicate better.