US ZIP codes are a type of postal code used within the United States to lớn help the United States Postal Service (USPS) route mail more efficiently.ZIP codes near me are shown on the map above.Some still refer to lớn ZIP codes as US postal codes. The term ZIP stands for Zone Improvement Plan. The basic 5-digit format was first introduced in 1963 & laterextended to địa chỉ an additional 4 digits after a dash to form aZIP+4 code. The additional 4 digits help USPS more precisely group mail for delivery. Though ZIP codes were originally developedfor USPS, many other shipping companies such as United Parcel Service (UPS), Federal Express (FedEx), DHL, & others make use of ZIP codes forsorting packages & calculating the time and cost of shipping a package (the shipping rate).

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Types of Zip Codes

Unique/single high volume address (ex. 20505 for the CIA in Washington, DC)PO Box only (ex. 22313 for the PO Boxes of Alexandria, VA)MilitaryStandard (all other ZIP codes)

Assignment of ZIP codes and Mail Sorting


The first digit of a USA ZIP code generally represents a group of U.S. States. The map of the first digit of zip codes above showsthey are assigned in order from the north east khổng lồ the west coast.The first 3 digits of a ZIP code determine the central mail processing facility, also called sectional center facility or "sec center", that is used lớn process andsort mail. All mail with the same first 3 digits is first delivered lớn the same sec center where it is sorted according to lớn the last 2 digits & distributed tolocal post offices. The sec centers are not mở cửa to the public and usually vì most sorting overnight. As you can see from themap of the first 3 digits of zip codes, the digits after the first are alsogenerally assigned from east lớn west. In the map, 0 is closer lớn white và 9 is much more vivid. It"s easy to lớn follow the gradient across each of the zoneseven though there are a few exceptions (such as the southwest tip of Georgia which uses 39XXX like central Mississippi).

The ZIP+4 code is not required, but it sida the post office in additional sorting of mail. A ZIP+4 code may correspond khổng lồ a thành phố block, group of apartments, oran individual high-volume receiver. It is also common for each PO Box number khổng lồ correspond to lớn a unique ZIP+4 code. Sometimes, several PO Box numbers are grouped intothe same ZIP+4 code by using the last several digits of the PO Box number. This method isn"t a universal rule though so the ZIP+4 must still be looked up for each POBox.

Places in the US so Remote, They Don"t Have a ZIP

As you can see from the map, not everywhere in the US is assigned a ZIP code. Remote và especially rural areas of the country vì not have enough deliverable addressesto create a mail route. Without mail delivery, a ZIP is not needed. If you are looking to get off the grid, these areas are some of the most remote places within the country.

USA ZIP Code Boundaries

Despite the fact that ZIP codes seem lớn be geographic in nature, that wasn"t their intended purpose. They are intended to group mail khổng lồ allow the USPS to lớn deliver mailmore efficiently. Some ZIP codes will span multiple states in order lớn make mail routing and delivery more efficient.In most cases, addresses in close proximity to each other are grouped in the same ZIP code which gives the appearance that ZIP codes are defined bya clear geographic boundary. However, some ZIP codes have nothing to vày with geogaphic areas. For instance, a single ZIP code is used for all US Navy mail.When ZIP codes appear to lớn be geographically grouped, a clear shape cannot always be drawn around the ZIP code because ZIP codes are only assigned lớn a point of deliveryand not the spaces betweendelivery points. In areas without a regular postal route or no mail delivery, ZIP codes may not be defined or have unclear boundaries.

US ZIP Code Map

No official ZIP code map according to lớn actual USPS data exists. The main issue is discussed above: there simply isn"t alwaysa clear geographic boundary for a ZIP code. The Census Bureau & many other commercial serviceswill try khổng lồ interpolate the data khổng lồ create polygons (shapes using straight lines) khổng lồ represent the approximate area coveredby a ZIP code, but none of these maps are official or entirely accurate.

On this site, all ZIP code maps use the ZIP Code Tabulation Areas (ZCTAs) as specified by the United States Census Bureau in 2010 (or newer) and discussed below.They provide a very close approximation of the area covered by a ZIP code. You can easily notice some of the boundary issues when viewing our maps.Very rural areas aren"t labeled as belonging to a ZIP code (such as much of Nevada & Utah) where there arefew, if any, addresses to deliver mail. If the address is on the same street as a ZIP code boundary on the map, be sure to search for the full streetaddress khổng lồ determine the ZIP code instead of relying on the map.

ZIP Code Tabulation Areas (ZCTAs)


ZIP code tabulation areas were developed by the United States Census Bureau. Their purpose is lớn convey statistical data about regions that are familiar tomost citizens. However, ZCTAs are not exactly the same as ZIP codes. As discussed above, it isdifficult to precisely define a geographic area covered by a ZIP code. ZCTAs were developed to tài khoản for some of the difficulties in assigning an area toa ZIP code & to precisely define a geographic area. Also, ZCTAs are not updated as frequently as ZIP codes. In general, they are updated once every10 years for the Census.

The Census assigns an area khổng lồ a ZCTA according lớn census blocks (the smallest geographic unit used by the census). Imagine a city blockthat makes up a typical census block as pictured khổng lồ the right. It is bounded on all 4 sides by portions of thành phố streets that each have their own nameand addresses. The issue is that census blocks almost always split down the middle of the street. ZIP codes rarely vì because that would requiretwo postal workers delivering mail to lớn that street - one for each side of the street. In the example, one mail carrier may deliver to lớn 3 sides of theblock via one ZIP code while another mail carrier delivers mail on the other street in a different ZIP code. When this happens, the Census Bureauwill assign the entire block to a single ZCTA (in this case, 21044) because the census block is the area that is precisely measured.If you are getting very precise (usually a matter of meters, not miles), census block boundaries near the edge of a ZIP code almost always split ZIP codes.

The statistics provided by the Census Bureau can give insight into the demographics within the ZIP code. For instance, see our ZIP code rankings.

Matching ZIP Codes with States, Counties, & Cities

Remember that ZIP codes were made to make mail delivery easier. They weren"t made khổng lồ correspond khổng lồ existing boundaries suchas cities, counties, or even states. If it is more efficient for a mail carrier khổng lồ drive across a state line lớn deliver mail, the ZIP code"boundary" will cross the state lines. ZIP codes don"t usually cross state lines, but some vì (65733, 71749, và 73949 are good examples).The complete các mục of ZIP codes that cross state lines is available as part of our US ZIP code list.

It gets even more complicated when trying to assign a ZIP code to lớn a specific county (as much as 25% cross county lines), congressional district,metro area, time zone, area code, etc. The edges of the boundaries commonly overlap. For the purposes of our không tính phí zipcode database by county downloads, we will commonly các mục either the most common region for the ZIP code or menu multiple regions if several exist in the ZIP code.

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For cities, the assignment is somewhat more complicated. USPS does not always use the city in which the ZIP code is located. The assignment ofcities to ZIP codes is more general. The đô thị is usually the name of the main post office. For instance, almost all ZIP codes in St. Louis County inMissouri have a city of Saint Louis when they may be more accurately described as the name of a smaller city where they are located.