Tips on ZIPs – Part II: The History US Postal Codes

Although ZIP codes may seem all too common and ubiquitous today, unless you can remember a time when mailing a letter cost you less than a nickel, you might not have known that ZIP codes were only first introduced in the 1960s with the introduction of new automated address reading machines. With rapid post-war growth across the country and the increasing volume of mail (which doubled between 1942 and 1962 from 33 billion to 66 billion pieces annually 1), and with the introduction of new “space age” technology to help sort the mail, the US Post Office Department launched a campaign to educate the public about its new Zonal Improvement Plan (ZIP) codes, and to encourage people to add the 5 digit number to the end of an address. And so, this guy was born…

Mr. ZIP was the first cartoon spokesperson to inform the country about how ZIP codes helped speed up the mail sending and delivery process with the slogan, “Mail Moves the Country, and ZIP Code Moves the Mail!”

Initially, the first postal zoning system had been developed during WWII, assigning 2-digit numbers to the largest metro areas across the country. That system was later expanded with the introduction of the 5-digit number in 1963, made mandatory in 1967, and extended to the ZIP+4 format in 1983, which is now the basis of the ZIP codes we know today. At the time of introduction, the 2-digit state abbreviations were also implemented to create space on the address labels for the new codes. Check out this list of older abbreviations, which had remained the same for nearly 90 years prior. ZIP codes today consist of 5 digits: the first 3 digits indicate the sectional center facility (regional sorting facility), and the last 2 specify your local post office. The +4 are non-mandatory, but they designate subsections of the larger area, specific city blocks, individual PO Boxes, and other special delivery cases. The first digit increases as “zones” move east to west across the country, from 0 in New England, to 9 in California. The map below shows these sectional ZIP code regions, but we’ll warn you, this is pretty much the closest there is to an “official” map! Stay tuned… next time we’ll tell you why ZIP codes are so hard to map, and why there’s really no such thing as a ZIP code boundary.
How Zip Codes Work

Plus, if you missed Part I of this series, be sure to go back and check it out. There’s a great ZIP Code music video, which is NOT to be missed.