What does “ZIP Code” refer
to?
A
ZIP Code is a five digit number that identifies a specific geographic mail
delivery area. The acronym ZIP refers to Zone Improvement Plan, a plan
implemented by the USPS in the early 1960’s to improve the sorting and delivery
of mail.
How many ZIP Codes are
there in the
There
are approximately 43,000 ZIP Codes in the
How many changes are made
to ZIP Codes monthly?
According
to the USPS, there are an average of 25,170 5-digit
ZIP Code changes on a monthly basis.
Where did ZIP Codes come
from?
In
the 1900’s and in the first half of the 20th century, mail was
primarily made up of social letters, which were transported by train throughout
the country. Rapid industrialization
changed the country and by 1963 business mail constituted 80% of the total
volume. This was a direct result of the
invention of the computer, which allowed companies to centralize accounts and
led to an explosion of bills, statements etc. that were delivered by mail.
On
July 1 in 1963 the Post Office began implementing a coding program aimed at
taking advantage of new transportation systems now available (namely highway
and air in addition to rail).
A
five-digit code was assigned to every address in the country. The first digit designated
a general area, from zero for the Northeast to nine for the far West. The next
two digits referred to one of the Sectional Center Facilities accessible to
common transportation networks. The final two digits designated small post
offices or postal delivery zones.
What is a three digit ZIP
Code?
This
refers to the first three digits of any ZIP Code. The first digit, 0-9 designates the general
area of the country with numbers starting lower in the east and increasing as
you move west. For example 0 covers
0
= Connecticut (CT), Massachusetts (MA), Maine (ME), New Hampshire (NH), New
Jersey (NJ), Puerto Rico (PR), Rhode Island (RI), Vermont (VT), Virgin Islands
(VI)
1
=
2
= District of Columbia (DC), Maryland (MD), North Carolina (NC), South Carolina
(SC), Virginia (VA), West Virginia (WV)
3
=
4
=
5
=
6
=
7
=
8
= Arizona (AZ), Colorado (CO), Idaho (ID), New Mexico (NM), Nevada (NV), Utah
(UT), Wyoming (WY)
9
=
What is the difference between a 3-digit ZIP Code and an
SCF?
An SCF (Sectional Center
Facility) is a postal facility that serves as the distribution and processing
center for post offices in a designated geographic area, which is defined by
the first three digits of the ZIP Code of those offices. This facility may
serve more than one 3-digit ZIP Code range.
3-digit
codes (ranges of ZIP Codes) refer to the first 3 digits of the 5-digit ZIP
Code. For instance, the ZIP Code 38104 has a 3-digit of 381. Any ZIP Code
starting with 381 would be grouped into this 3-digit area.
How many 3-digit ZIP Codes
are there?
There
are 929 3-digit ZIP Codes in the country.
Do other countries have ZIP
Codes?
While
other countries do have methods for distributing mail by regional code, they do
not have ZIP Codes exactly as the USPS defines the term. For example, Canadians rely on “FSALDU”,
where the FSA is similar to a US ZIP Code and the LDU is more akin to a US
ZIP+4.
Are there different kinds of
ZIP Codes?
The
USPS differentiates ZIP Codes as standard and unique. A standard ZIP Code is one that is an
established and usual ZIP Code, while an unique ZIP Code is one that only
delivers to one specific large entity (such as a hospital or university).
What does “Unique” mean
when referring to a ZIP Code?
A
unique ZIP Code is a ZIP Code which includes only addresses within one specific
large entity, for example a university, air force base or other large mail generating
organization.
Do ZIP Codes for P.O. Boxes
change?
No,
these generally do not change.
What is
a ZIP+4 Code?
This
refers to the 5-digit ZIP code plus a 4-digit add-on number which identifies a
geographic segment within the 5-digit delivery area, such as a city block,
office building, individual high-volume receiver of mail, or any other distinct
mail unit. The purpose of +4 codes is
to aid efficient mail sorting and delivery. Business mailers are the primary
users of ZIP+4’s, because mailers who mail in bulk on the ZIP+4 or carrier
route level can receive rate discounts.
Can
ZIP Codes cross State, County, political jurisdictions (cities, congressional
district), and metro areas?
In short, the answer is yes to all of the
above. ZIP Codes rarely cross state
lines, but cross county lines as often as 10%. You can see this yourself by
viewing a sample ZIP code map
About ZIP Code Mapping
How are boundaries for ZIP Codes
defined?
The
USPS does not define boundaries for ZIP Codes. Instead ZIP Codes represent
clusters of addresses, grouped into these units for efficiency of
delivery. In most cases ZIP Codes
resemble spatial areas since they comprise spatially proximate street
ranges. However, this is not always the
case. In rural areas, ZIP codes can be
collections of road lines (rural delivery routes) that in reality do not look
much like a closed spatial area.
To
map ZIP Codes with precise boundaries, as we often see them represented, the
data provider essentially draws a line around all of the street segments
encompassing addresses belonging to each code.
What is the difference
between ZIP Code data provided by the USPS for free and that provided by a
mapping service?
The
USPS does not maintain or release ZIP Code maps; it only releases ZIP Code
correspondence information in database format. Commercial vendors then take
each ZIP Code’s information and attach it to a polygon that represents the
dimensional area covered by that ZIP Code.
Each polygon is then placed at the correct longitude and latitude within
a map framework – thereby creating ZIP Code maps. The resulting ZIP Code map data is then
integrated with other map software in a GIS system to be used in creating
detailed multi-layered ZIP Code-related maps.
Are P. O. Boxes included in
the mapping of ZIP Code boundaries?
P.O. Box ZIP Codes generally represent postal
patrons from a diverse geography base (with some often being out of state or
even country). These ZIP Codes are
typically not included in ZIP Code mapping.
What is a ZIP Code centroid?
A
ZIP Code’s centroid is a point near the center of the
areas of a polygon for a 5-Digit ZIP Code.
The centroid is calculated as the internal
balance point, based on the coordinate extremes of the polygon. In cases where
the polygon is irregular, the centroid may be
adjusted so that ZIP Code labels never fall outside of the polygon.
Do carrier routes follow
ZIP Codes?
Each
carrier route is explicitly defined as part of a single ZIP Code. The full 9 digits of the carrier route code
(e.g. 12508C007) is a unique code that defines each carrier route and so it
cannot cross multiple ZIP Codes.
Why do companies use ZIP
Code maps for direct mailing?
Companies eager to capitalize on the USPS discounts for bulk
mailing by ZIP Code and carrier routes need ZIP Code maps in order to determine
which ZIP Codes cover which neighborhoods. ZIP Codes have
also been adopted by marketing people and by all kinds of other researchers as
a standard geographic area, similar to a county or state. Therefore ZIP Code maps can be helpful for
sales territory creation and management, and other custom applications.
Who provides ZIP Code
maps? Can’t I get a ZIP Code map from
the USPS?
The Postal Service does not maintain ZIP Code maps. Mapping ZIP Codes is challenging, especially
because the delivery routes they represent are always changing. The
USPS sends visitors to USPS.com looking for ZIP Code maps
to Maponics and the Maponics
Online Store.
How can I tell if a ZIP
Code map is accurate and useful?
Because
the delivery areas that ZIP Codes represent are constantly changing the primary
concern in purchasing a ZIP Code map should be making sure that it has been
updated at least within the past six months.
Are there areas of the
nation that don’t have ZIP Codes?
Yes,
in extremely rural areas where there is no mail delivery
(deserts, mountains, lakes, most of Nevada) ZIP codes are not defined.
Mailing by ZIP Code
What is a ZIP Code bulk
mailing?
The
term "bulk mail" refers to quantities of mail prepared for mailing at
reduced postage rates. The post office
offers reductions in postage for customers who are willing to share in the
preparation work required to send a mailing.
In order to conduct a bulk mailing, the mailer must be sending to more
than 200 addresses within one ZIP Code.
Other
requirements for mailing at bulk rates include:
Your
discount depends on the mailing service you choose and the work you do. For
example, if you mail 1,000 letter-sized flyers to everyone in your ZIP Code, it
would cost $0.41 per piece for retail First-Class postage, or $410. If you mail 1,000 flyers using Standard Mail
to everyone in your ZIP Code by adding a barcode, sorting them by carrier
route, and entering them for mailing at the appropriate sectional center
facility, you might pay as little as $0.135 per piece, or $135. Letter shops
and mail houses are experts in preparing mail for bulk mailings, and can be
very helpful in figuring out how to save money.
Why does the USPS offer
discounts for bulk mailings by ZIP Code?
Bulk
mailing requires the customer to take on some of the labor typically executed
by postal service employees (preparing, sorting and entering your mail). The post office rewards bulk mailers by
sharing their labor savings through reduced postage rates.
Discount
rates are not available for Express Mail or Priority Mail.
Are there ways to mail to
just a portion of a ZIP Code and still get a saturation discount?
Yes. The steepest discounts offered by the USPS
are for mailing by carrier route. Click
here to learn more about mailing by
carrier route.
Who normally mails by ZIP
Code?
Business
mailers whose target readers are usually concentrated in one small town or
neighborhood are best served by mailing by ZIP Code.
Are demographics available
by ZIP Code?
The
U.S. Census Bureau collects demographic data and makes it widely available to
the public. However it is released using
Census geography measures such as block groups and census tracts, rather than postal geography. There are companies that are able to convert
the data so it is viewable by ZIP Code and other postal geography, so that it
can be used for marketing purposes.