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On this day in 1963, the U.S. Post Office Department asked Americans to do something they have never particularly enjoyed: learn a new system and start using it immediately. It was called a ZIP code, and it would usher in the age of electronic mail sorting. Americans hated it.

Five-digit ZIP (Zone Improvement Plan) codes were the brainchild of postal inspector H. Bentley Hahn, who built on an idea from postal employee Robert A. Moon. Moon divided the country into roughly 900 geographic areas and assigned them three digits; Hahn took it a step further. The digits represented the national region, subregion, post office, and delivery station.

The idea certainly wasn’t new: London was experimenting with postal zones back in the 1850s.

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The average piece of mail in the United States was passing through 17 stops. Following World War II, the Post Office Department was handling about 30 billion pieces of mail each year. The system could not keep up.

The post office introduced a plan to fix it. But first it had to convince the reluctant public, who’d barely gotten used to telephone area codes. To some, ZIP codes felt like a Cold War conspiracy in the making. Americans bristled at being reduced to numbers and having to learn the numbers assigned to their correspondents.

Fun Fact

Ukraine was the first country to implement a system of modern-day postal codes, in 1932.

It fell on thousands of local post offices to implement the new system in their communities, and it took almost three years for enough people to embrace ZIP codes for electronic scanning to be widely deployed. But once those mechanized optical scanners got going, they could fly, sorting 36,000 pieces of mail each hour. Some counties reported $10,000 a year in savings (more than $100,000 today), mail was arriving up to 48 hours sooner, and zero jobs were lost.

It took until the end of the decade for people to fully get on board the mail truck with ZIP codes (and it took a little help from Santa—his new ZIP code was widely advertised so that children writing letters to him would become early adopters).

And just when we’d gotten used to that, in 1983 the USPS added the ZIP+4.

By the Numbers
  • ~38,000: Zip codes in America now
  • 99701: Santa’s original ZIP code
  • $10 billion: Estimated value ZIP codes add to the U.S. economy annually
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