Although written letters may be becoming a less popular medium of communication than email and cell phones, there will likely be a need for mail delivery for the foreseeable future—and thus, a need for zip codes. But besides potentially determining property taxes, what do zip codes really mean and why do we have them?

Zip codes are actually a much more recent phenomenon than you might believe. In fact, they're only 52 years old—a concept that was introduced during World War II, and officially implemented in 1963. The zip (Zoning Improvement Plan) code was created when the postal service lost a huge portion of their staff who went to fight in the war. Because of this, they needed a simple way to help the understaffed postal service deliver mail effectively.

Initially, the zip code was only a two-digit number: the first denoted the city, the second denoted the state. But as the need for delivery expanded, so did the concept of the zip code. As of 1963, zip codes' numbers are determined by a few factors: the area, the regional postal facility and the local zone.

The first number of the five-digit code signifies the region which the address is located in, a number that grows from the east coast to the west. For example, Eastern states such as Maine and New York begin with 0 or 1, whereas the Western states of California and Washington begin with a 9. The second two digits in the code determine a smaller region within each initial area that translates to a central post office facility for that area. The final two digits signify the local post office of the address.

You may have noticed that zip codes often have a hyphenated four-digit number on the back end which is rarely used. This annex was created to help further specify addresses, but according to Business Insider, the creation of sorting and location technologies removed the need for the additional four numbers. The final numbers further specified the location of the delivery area.

[via Business Insider]

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