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How did ZIP Codes start and what makes up a ZIP Code?	ZIP Code look-up	ZIP Code Resources
U.S. Zone Chart	ZIP Code Changes

How did ZIP Codes start and what makes up a ZIP Code?

• History of the ZIP Code

  In the early 1960’s, the mail being processed by the then Post Office Department had changed dramatically. Prior to this time, the majority of mail was domestic related.  Now, approximately 80 percent of the mail was business related. Changes had to be made to the way mail was processed and delivered.

In June 1962, the presidentially appointed Advisory Board of the Post Office Department, after a study of its overall mechanization problems, made several primary recommendations. The Board recommended that the Department give precedence to the development of a coding system, an idea that had been under consideration in the Department for a decade or more.

Throughout the years, a number of potential coding programs had been examined and discarded. Finally, in 1963, the Department selected a system advanced by department officials, and, on April 30, 1963, Postmaster General John A. Gronouski announced that the ZIP Code would begin on July 1, 1963.

By July 1963, a five-digit code had been assigned to every area in the country. The first digit designated a broad geographical area of the United States, ranging from zero for the Northeast to nine for the far West. This was followed by two digits that more closely pinpointed population concentrations and those sectional centers accessible to common transportation networks. The final two digits designated small post offices or postal zones in larger zoned cities.

ZIP Code began on July 1, 1963, as scheduled. Use of the new code was not mandatory at first for anyone, but, in 1967, the Post Office required mailers of second- and third-class bulk mail to presort by ZIP Code. Although the public and mailers alike adapted well to its use, it was not enough.

In 1983, the Postal Service™ began using an expanded ZIP Code called "ZIP+4®." A ZIP+4 Code consists of the original 5-digit ZIP Code plus a 4-digit add-on code. The 4-digit add-on number 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 unit that would aid efficient mail sorting and delivery. Use of the 4-digit add-on is not mandatory, but it helps the Postal Service direct mail more efficiently and accurately because it reduces handling and significantly decreases the potential for human error and possibility of misdelivery. ZIP+4 is intended for use primarily by business mailers who prepare their mail with typewritten, machine-printed, or computerized formats that can be read by the Postal Service's automated scanners during processing.

• What is a ZIP Code?
• ZIP is an acronym that stands for "Zone Improvement Plan."
• ZIP Code numbers are extremely important in the processing and delivery of mail.
• Using the correct ZIP+4 Code reduces the number of handlings and significantly decreases the potential for error and possibility of misdelivery.
• What do the parts of a ZIP Code mean?
  

The nine digits of a ZIP+4 code (e.g., 12345-6789) may be grouped as follows: [123] [45] [67] [89]

• [123] : Sectional Center or Large City
• [45] : Post Office facility or Delivery Area
• [ - ] : The required "dash" or "hyphen" separates the first five digits from the last four digits; the +4
• [67] : Sector or Several Blocks
• [89] : Segment or One Side of a Street
• Is the hyphen in a ZIP+4 ZIP Code number required?

Yes, when using a ZIP+4 ZIP Code, the number must consist of five digits, a hyphen (or dash), and four digits. Improperly labeled mailpieces may progress slower through the mail system and may be returned to sender if the United States Postal Service® is unable to deliver the item.

• ZIP Code Type Definitions
• Standard: It is the established and usual ZIP Code used in a specified area.
• PO Box™ Only:  A ZIP Code that is assigned only to a set of PO Boxes at a particular facility.
• Unique: Assigned to a company, government agency, or entity with sufficient mail volume, based on average daily volume of letter size mail received, availability of ZIP Code numbers in the postal area, and USPS cost-benefit analysis.
• Military:  A ZIP Code assigned to a US Military installation APO/FPO/DPO.
• Who is Mr. Zip?

On July 1, 1963, the United States Postal Service® implemented the ZIP (Zone Improvement Plan) Code to improve the sorting and delivery of mail and prepare the way for better, faster, automated processing of mailpieces. The character Mr. ZIP was designed to promote adoption of the new ZIP Code™ (see image below).

 

• How many ZIP Codes are there?

The number of ZIP Code™ areas in use is constantly being revised. Currently there are over 42,000 ZIP Codes in use.

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ZIP Code look-up

• How can I find a ZIP Code or ZIP+4 ZIP Code online?

  A domestic ZIP Code number and other ZIP Code information (including ZIP+4 Codes) can be found through the Look UP a ZIP Code tool on the usps.com® web site. Expand the Quick Tools that appears on the left of the page and select “Look Up a ZIP Code”.  A small dialog window will open that will allow you to search for a ZIP+4 Code by address or a ZIP Code by city and state.  Simply fill in the appropriate fields (marked with a red asterisk) and then click the “Find” button.

• How can I find a ZIP Code or ZIP+4 ZIP Code offline?

  Customers seeking offline address-matching solutions can search the list of certified vendors and licensees on usps.com.

• How do I find the city name associated to a ZIP Code?

  To find the city name associated with a specific ZIP Code™, select the “Look Up a City by ZIP Code” option from the Look UP a ZIP Code tool on USPS.com.  Expand the Quick Tools that appears on the left of the page and select “Look Up a ZIP Code”.  The option for finding city name associations can be found under the “More lookup options” dropdown link.  After expanding this dropdown, click on the button that appears with the title “Look Up a City by ZIP Code”.  From here you may simply enter the ZIP Code, and click the “Find” button to see all of the recognized city named associations for an entered ZIP Code.

• Where can I access county or other detailed mailing industry information about an address?

  To find county or other detailed delivery information for an individual address, you will need to use the full-page version of our online Look UP a ZIP Code tool on USPS.com.  The full-page version of the Look UP a ZIP Code tool may be accessed from the Quick Tools menu on the left of the page of the USPS.com web site.  From this menu, Click on “Look Up a ZIP Code”, then from the small dialog window that appears, click on the link “Go to full-page version”.

Once on the full-page version of the Look UP a ZIP Code tool, perform the following steps:

1. Type in an Address including the City, State and/or ZIP Code.
2. Click “Find”
3. The application will attempt the entered address with one or more from our database.  The matching addresses will appear in the  results.
4. Underneath this information (directly below the city name), click on the “Show Mailing Industry Details” link
5. Detailed mailing industry information including specific county information will be displayed for the address
   

• Where can I find an international/foreign ZIP Code (Postal Code)?

The U.S. Postal Service does not keep information on Foreign Postal Codes (similar to the ZIP Code used in the USA), or other specific information such as the price of postage for items sent from other countries. For the Postal Service to deliver mail to a foreign country, we only need the name of the destination country. For postal code information for a foreign country, it is recommended that you contact the country in question or look for further information about that country's postal codes on the internet.

• My street name is misspelled in the ZIP Code Look-up tool on usps.com.  How can this problem be fixed?

You should contact your local Post Office and request their assistance in resolving the problem.  All information in our national ZIP Code database is maintained by the Address Management System (AMS) Office. The local Post Office can contact the AMS Office and request the street name to be corrected.

• Why will the ZIP Code Look-up tool not acknowledge the address that I entered?

  The address may have been entered incorrectly, is an invalid address, or it may be an address assigned to a new housing development.  Verify that the address you have is correct and re-enter it in the ZIP Code lookup tool. If you still do not get a response and the address is a valid mailing address, contact the local Post Office and request their assistance in resolving the problem. New addresses will take between 7 to 14 days to appear on the USPS.com Look Up a ZIP Code tool.

  Note:  Some addresses in Wisconsin and New Mexico have a letter prefix as a direction indicator (e.g. “N”) and may include another letter within the street number of the address.  This numbering system is similar to grid numbering but spaces are omitted between the letters and the numbers.

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ZIP Code Resources

• Is there a Five-Digit ZIP Code and Post Office Directory Available?

  Printed copies of the National 5-Digit ZIP Code™, Post Office™, and ZIP+4 State Directories have been discontinued. This valuable information is now available in the Address Information System Viewer (AIS). The AIS Viewer is an interactive CD-ROM designed to provide the ability to retrieve, view, and print accurate and current ZIP Code information for all 50 states on request. 

For more information on the AIS View, please contact the National Customer Support Center at 1-800-238-3150, Option 6 and then Option 2 to speak to a customer service representative.

• Can I get a ZIP Code map from the United States Postal Service?

The United States Postal Service does not maintain ZIP Code™ maps, and the only related product we currently offer at this time is the TIGER/ZIP+4 File. This file relates ZIP+4 codes to Census Bureau data (e.g., latitude, longitude, Standard Metropolitan Statistical Area (SMSA), etc.). For more information about the TIGER/ZIP+4 File, call the National Customer Support Center at 1-800-238-3150, select “Option 6”, and then “Option 2”.

In addition, there are many commercial software products available with geographic information. Check with your local software store or search the Internet for related websites.

• Note: Some postmasters may have ZIP Code maps covering their local area of responsibility. These maps are often obtainable from them free of charge and are usually published in the Yellow Pages of local telephone directories in most large metro areas.

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U.S. Zone Chart

• What is a National Zone Chart and how can I obtain one?
  

  The Official National Zone Charts identify the appropriate distance code assigned to each origin and destination ZIP Code pairing for every ZIP Code number in the nation. These distance codes, referred to as zones, are designated as "Local" and "1 through 8".

• Zone charts create a matrix for each originating ZIP Code number with the following (matched) information:
  1. Destination ZIP Code range.
  2. Associated zone for the distance.
     

  Zone charts are produced by the United States Postal Service using geological survey files of established latitude and longitude coordinates to determine the distance between origin and destination ZIP Code pairings.

Postage meters also use these charts to determine printed postage. Any questions on these must be answered by the manufacturer of the meter.

If you want to purchase a complete set of Official National Zone Charts (which are available on electronic media and/or hard copy), please contact the National Customer Support Center at 1-800-238-3150, select Option 6.

To calculate the zone chart based on the first 3 digits of any ZIP Code number you may use the Postal Zone Chart lookup tool (free of charge) at Zone Charts.

•  Configuration of the Zone Chart

  The Official National Zone Charts identify the appropriate distance code assigned to each origin and destination ZIP Code pairing for every ZIP Code number in the nation. These distance codes, referred to as "zones", are designated as "Local" and "1 through 8".

  The Local Zone applies to mail deposited at any Post Office for delivery to locations within the delivery area of that Post Office. For various types of Post Offices, the local zone applies to all mail that both originates and is destined within:

  • The 5-digit ZIP Code area(s) assigned to the same post office
  • Any of the 5-digit ZIP Codes that are part of any unique 3-digit ZIP Code prefixes or other separate 5-digit ZIP Code(s), as applicable, assigned to the same post office.

Check with your local Post Office for specific details regarding your area.

Non-Local Zones are defined by zone as follows:

Zone 1 includes all units of area outside the local zone lying in whole or in part within a radius of about 50 miles from the center of the area. Below is a listing of each zone and the defined coverage area:

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 ZIP Code Changes

• Why does a ZIP Code Change?

  Occasionally the United States Postal Service will add new or realign existing ZIP Code areas to accommodate population growth and operational needs.

• New ZIP Codes are announced publically by the District Office approximately thirty (30) days before the ZIP Code change goes into effect.
• Most large mailers (i.e., credit card or utility companies) subscribe to Postal Service products that will reflect the ZIP Code change within three (3) to six (6) months from the effective date.
• Friends, family and smaller businesses will have to be notified individually.
• Mail with the old ZIP Code will continue to be delivered for one year.

Additional Notes:

• Realignment may include the temporary or permanent removal of a current ZIP Code.
• ZIP Codes for Military (APO/FPO) areas may be made active or inactive as mail volume to these areas fluctuates.
  
  
• Will a ZIP Code for a Post Office Box change?

Although ZIP Codes will vary for PO Boxes from city to city, ZIP Codes for PO Boxes within the same city usually do not change, though the ZIP+4 will likely include a code in the plus four that designates the actual Post Office Box. For further information regarding this, contact the local Post Office.

• The ZIP Code where I live changed recently.  Why does the ZIP Code look-up information on usps.com not reflect this change?

The ZIP Code lookup site on usps.com may not have been updated yet. All information in our national ZIP Code database is maintained by a local Address Management System (AMS) office. Any changes, corrections, or updates to the national database will be reflected in the ZIP Code lookup tool on usps.com within fourteen (14) days.

What is the ZIP Code Boundary Review Process?

• General Policy

The ZIP Code system was created and designed to provide an efficient postal distribution and delivery network. ZIP Code assignments are, therefore, closely linked to factors such as mail volume, delivery area size, geographic location, and topography, but not necessarily to municipal or perceived community boundaries. The general stability of boundaries is essential to prompt and accurate distribution of mail. However, delivery growth and changing demographics can necessitate adjustments to ZIP Code boundaries in order to achieve United States Postal Service objectives.

While the Postal Service must be guided by concerns for service and efficiency, it does appreciate the identity and addressing concerns of local communities. Therefore, municipal requests to modify authorized last lines of address and/or ZIP Code boundaries in order to provide municipal identity, especially in undeveloped areas, will be considered and every reasonable effort will be made to accommodate them.

A community group may also request an adjustment to a ZIP Code boundary, as outlined in this policy. The requested boundary should be consistent with the actual municipal boundary and identity of the affected area. Documented endorsement of the request by the local government is strongly recommended. This will help to ensure that the non-postal interests of all customers are represented fairly and are in concert with long-term municipal planning.

Requests to amend postal ZIP Code boundaries must receive careful, thorough and balanced evaluations. The unique situations pertinent to each ZIP Code boundary must be considered. Administrative solutions that do not adversely affect postal operations should be pursued to the maximum extent practicable. Realignment of a ZIP Code boundary should be considered only where there are no viable administrative solutions and no unreasonable impacts to postal operations.

• Responsibilities

Proponents (Municipalities and community groups):
Submit the specific change(s) desired, with any rationale and justification, in writing to the District Manager who would be responsible for the affected territory if the change were approved. If the request is later denied, the decision may be appealed, unless denial was based on a negative customer response to a survey conducted in accordance with this process. The basis of consideration of an appeal will be limited to whether or not reasonable accommodation was made by local postal managers. Appeals must be made within forty-five (45) days of the issuance of the District Manager's final decision and submitted to:

MANAGER, DELIVERY
U.S. POSTAL SERVICE
475 L'ENFANT PLAZA SW RM 7142
WASHINGTON, DC 20260-2802

Local Postmasters:
If requests are received locally, forward them to the district for appropriate consideration. Provide background and operational information pertinent to the evaluation of the request.

District Managers: Operations Programs Support will normally process all requests concerning addressing and ZIP Code boundaries. On receipt of a request, notify affected postmasters, obtain background material and:

• Identify all issues
• Identify potential administrative solutions
• Determine specific impacts and the operational feasibility of the request
• Quantify impacts
• Provide detailed supporting documentation
• Review findings with the affected postmasters
• Meet with the proponent to discuss the issues, impacts, and potential alternatives. If partial accommodation is feasible, the proponent may wish to amend the request.
• Prepare a recommendation

A final determination should be provided within sixty days of receipt of the request. However, depending on the magnitude of potential changes and/or the number of pending requests, some extension or prioritization may be necessary. If a determination is not expected within sixty (60) days, notify the proponent of the estimated completion date.

The District Manager will make a decision to authorize alternative solutions, and/or to grant or deny any realignment. If the proposal is denied, the District Manager must advise the proponent in writing, giving the specific reasons for denial. The response must be based on the results of the analysis and must advise the proponent of the appeal process.

If accommodation is being considered, advise the affected postmaster(s) and arrange a joint meeting with the proponent to discuss the proposed accommodation. If agreement is reached, proceed with the customer survey element of the process.

Vice President, Area Operations:
The Vice President, Area Operations must review all cases that are appealed; validate the data used to support the decision; ensure that a thorough and reasonable evaluation was conducted; and provide a written decision to the Headquarters Manager, Delivery.

Headquarters:
The Manager, Delivery administers the ZIP Code Boundary Review Process. A proponent whose request has been denied as a result of this process may appeal that decision to the Manager, Delivery, except where a potential accommodation was agreed to, but was not implemented due to a negative customer survey response.

On receipt of an appeal, Headquarters will obtain the case file from the District. The basis of consideration will be limited to whether or not reasonable accommodation was provided. Generally, a decision will be provided within sixty (60) days.

To ensure the stability in the ZIP Code network, facility planning and postal operations, once a request to match a municipal boundary has been accommodated, additional requests to amend the boundary will not be considered more frequently than once every ten years.

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