What is a ZIP Code?
A ZIP code is a numbering system with separate code numbers for all cities
in the United States. Visual example:5 digit ZIP code maps
illustrate the various zip code states, towns, and counties in the U.S..
On April 30, 1963, Postmaster General John A. Gronouski announced that
the ZIP Code would begin on July 1, 1963. The United States Post Office
Department introduced the Zone Improvement Plan (ZIP) Code, a coding
system that assigned codes on maps to all addresses in the country.
1943 the United States Post Office Department divided cities into zones to
assist in speeding sorting and mail delivery. By July
1963, a five-digit zip code had been assigned to every address throughout
the United States map.
What do the ZIP Code Digits Stand For?
There are five digits in the original ZIP Codes. The first digit indicates
one of ten large geographic areas in the country, ranging from zero in
the Northest to nine in the far West. The second
digits indicate metropolitan areas and sectional centers accessible
to common transportation.The fourth and fifth ZIP Code digits indicate
local post offices or postal zones in larger cities.
How are ZIP Codes used by the Post Office?
This new Zoning Improvment Plan coding system made it necessary to establish
large transportation centers throughout the country to relieve major
metropolitan post offices
of the burden of processing all the mail.
In 1965, a high-speed optical reader was introduced by the United States
Post Office Department. This machine could sort mail by reading the ZIP
Code automatically. They read the address and printed a
bar code on the envelope that corresponded to them. At destination post
offices, a bar code sorter then read the bar code and sorted the letters
and address into appropriate holding areas to await delivery.
Sectional centers are where most mail is processed. A letter mailed at
your local post office may be delivered to a sectional center if it isn’t
destined for delivery within the same ZIP Code as you mailed it. Before
delivery to local post offices for mail carriers to distribute mail to
its final destination, automated systems sort the mail and postmark it.
For more information about the automation
of the United States Postal Service, please see our article on ZIP Codes
Zip Codes Plus: The ZIP + 4 Code
In 1983, the United
States Postal Service expanded the ZIP Code system to include four
more digits. This is called the ZIP
+ 4 Code. The additional digits identify even more precisely
the mail’s destination. According
the the United States Post Office, the new sixth and seventh digits
indicate a “delivery sector, such as several blocks, a group
of streets, a group of post office boxes, several office buildings, or
a small geographic area. The last two numbers denote a delivery segment,
might be one floor of an office building, one side of a street between
intersecting streets, specific departments in a firm, or a group of post
This new ZIP + 4 Code speeded up mail handling by reducing the number of
times a letter had to be handled, and reducing the time mail carriers
spent placing their mail in the order of delivery. A multiline Optical
Character Reader reads the address, then sprays a barcode representing the
plus two additional digits indicating the exact delivery street address.
Using this barcode database, it can sort the mail in the correct sequence for
each carrier’s delivery route.
The Importance of the Correct ZIP Code
The United States Postal Service emphasizes the importance of addressing
your mail correctly in order to
assure timely delivery. According to the Postal Service, “Using the
correct ZIP Code helps to direct your mail more efficiently and accurately.” They
suggest you use a site such as zip-codes.com to
obtain the correct ZIP Code, as well as the correct spelling of the City
and State. If you
need to get a ZIP Code and don’t have access to the Internet, you
can call 1·800·ASK·USPS and get it by phone. Using zip code
maps can also help and may save you a dime on the call.