ZIP codes were introduced in 1963 to allow for quicker mail sorting. The rarely used ZIP code plus four was later introduced in 1983.
To decode your five-digit ZIP code, look to the first number. That number represents a general geographic zone in the U.S. The numbers progress from zero to nine moving east to west. So ZIP codes range from 00501 in Holtsville, New York, to 99950 in Ketchikan, Alaska.
The next two numbers indicate a more specific regional area, and the final two numbers a nearby post office or postal zone.
Now for some rapid-fire fun ZIP code facts: ZIP stands for Zoning Improvement Plan. The simplest ZIP code is none-other than General Electric in Schenectady, New York — 12345. ZIP code 10025 in Manhattan, New York City, is the ZIP code with the most possible deliveries with 46,167. And ZIP codes are used for more than mail. They are integral to the functioning of the nation’s 911 emergency system too.
To find out more on the history of the Postal Service, look no further than this history of the Postal Service in fast facts and historical photos.