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A 1974 postage stamp encouraging people to use the ZIP Code on letters and parcels

AZIP Code(an acronym forZone Improvement Plan[1]) is a system ofpostal codesused by theUnited States Postal Service(USPS). The termZIPwas chosen to suggest that themailtravels more efficiently and quickly[2](zipping along) when senders use the code in thepostal address.

Introduced on July 1, 1963, the basic format comprised five digits.[3]In 1983, an extended code was introduced namedZIP+4;it included the five digits of the ZIP Code, followed by a hyphen and four digits that designated a more specific location.

ZIP CodeandZIP+4are registered trademarks of the United States Postal Service, which also registeredZIP Codeas aservice markuntil 1997.[4]

History

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Early postal zones

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A 1963 U.S. Post Office sign featuringMr. ZIP
Alabelinside astamp bookletpromoting the ZIP Code
A Swingin' Six video used by the post office to promote the ZIP Code

The early history and context of postal codes began withpostal district/zone numbers.TheUnited States Post Office Department(USPOD) implemented postal zones for 178 large cities in May 1943.[5]Postmaster GeneralFrank Walkerexplained that many experienced postal clerks were going into the army, and the zone system would enable inexperienced clerks to sort mail without having to learn the delivery area of each city carrier.[6]

For example:

Mr. John Smith
3256 Epiphenomenal Avenue
Minneapolis16,Minnesota

The "16" is the number of the postal zone in a specific city.[7]

Establishment

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By the early 1960s, a more organized system was needed, and non-mandatory five-digit ZIP Codes were introduced nationwide on July 1, 1963. The USPOD issued itsPublication 59: Abbreviations for Use with ZIP Codeon October 1, 1963, with the list oftwo-letter state abbreviationswhich are generally written with both letters capitalized.[8]An earlier list, publicized in June 1963, had proposed capitalized abbreviations ranging from two to five letters.[8]According toPublication 59,the two-letter standard was "based on a maximum 23-position line, because this has been found to be the most universally acceptable line capacity basis for major addressing systems",[8]which would be exceeded by a long city name combined with a multi-letter state abbreviation, such as "Sacramento, Calif." along with the ZIP Code. The abbreviations have remained unchanged, with the exception ofNebraska,which was changed from NB to NE in 1969 at the request of theCanadian Post Office Department,to avoid confusion withNew Brunswick.[8]

Robert Moonis considered the father of the ZIP Code; he submitted his proposal in 1944 while working as apostal inspector.[9][10]

The phrase "zone improvement plan" is credited toD. Jamison Cain,a Postal Service executive.[11]The post office credits Moon with only the first three digits of the ZIP Code, which describe thesectional center facility(SCF) or "sec center". An SCF is a central mail processing facility with those three digits. The fourth and fifth digits, which give a more precise locale within the SCF, were proposed by Henry Bentley Hahn Sr.[12]

The SCF sorts mail to all post offices with those first three digits in their ZIP Codes. The mail is sorted according to the final two digits of the ZIP Code and sent to the corresponding post offices in the early morning. Sectional centers do not deliver mail and are not open to the public, although the building may include a post office that is open to the public, and most of their employees work thenight shift.Items of mail picked up at post offices are sent to their own SCFs in the afternoon, where the mail is sorted overnight. In the case of large cities, the last two digits as assigned generally coincided with the older postal zone number.[7]

For example:

Mr. John Smith
3256 Epiphenomenal Avenue
Minneapolis, MN55416

In 1967, these became mandatory for second- and third-class bulk mailers, and the system was soon adopted generally. The United States Post Office used acartoon character,which it calledMr. ZIP,to promote the use of the ZIP Code.[13]The name "Mr. ZIP" was coined by D. Jamison Cain.[11]Mr. ZIP was often depicted with a legend such as "USE ZIP CODE" in theselvageof panes ofpostage stampsor on the covers of booklet panes of stamps.[13]Mr. ZIP was featured prominently alongside musical group "The Swingin' Six" in a variety show that the post office used to explain the importance of using ZIP Codes.[14]

ZIP+4

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In 1983, the U.S. Postal Service introduced an expanded ZIP Code system that it namedZIP+4,often known as "plus-four codes", "add-on codes", or "add-ons". A ZIP+4 Code uses the basic five-digit code plus four additional digits to identify a geographic segment within the five-digit delivery area, such as a city block, a group of apartments, an individual high-volume receiver of mail, a post office box, or any other unit that could use an extra identifier to aid in efficient mail sorting and delivery. However, the new format was not adopted universally by the public; it eventually became obsolete with modern technology.[15]In general, mail is read by amultiline optical character reader(MLOCR) that almost instantly determines the correct ZIP+4 Code from the address—along with the even more specificdelivery point—and sprays anIntelligent Mail barcode(IMb) on the face of the mail piece that corresponds to 11 digits—nine for the ZIP+4 Code and two for the delivery point.

Forpost office boxes,the general but not invariable rule is that each box has its own ZIP+4 Code. The add-on code is often one of the following: the last four digits of the box number (e.g. PO Box 107050, Albany, NY 12201-7050), zero plus the last three digits of the box number (e.g., PO Box 17727, Eagle River, AK 99577-0727), or, if the box number consists of fewer than four digits, enough zeros are attached to the front of the box number to produce a four-digit number (e.g., PO Box 77, Juneau, AK 99750-0077). However, there is no uniform rule, so the ZIP+4 Code must be looked up individually for each box (e.g. using the USPS's official ZIP Code Lookup tool, and being sure to enter just city and state, not the 5-digit ZIP).[16]

Postal bar code

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The ZIP Code is often translated into an Intelligent Mail barcode that is printed on the mailpiece to make it easier for automated machines to sort. A barcode can be printed by the sender (some word-processing programs such asWordPerfect[17]include the feature), but this is not recommended, as the address-to-ZIP lookup tables can be significantly out of date.

Customers who send bulk mail can get adiscounton postage if they have printed the barcode themselves and have presorted the mail. This requires more than just a simplefont;mailing listsmust be standardized with up-to-dateCoding Accuracy Support System(CASS)-certified software that adds and verifies a full, correct ZIP+4 Code and an additional twodigitsrepresenting the exactdelivery point.[citation needed]Furthermore, mail must be sorted in a specific manner to an 11-digit code with at least 150 mailpieces for each qualifying ZIP Code and must be accompanied by documentation confirming this. These steps are usually done with PAVE-certified software that also prints the barcoded address labels and the barcoded sack or tray tags.[citation needed]

The assignment of delivery point digits (the 10th and 11th digits) is intended to ensure that every single mailable point in the country has its own 11-digit number. The delivery-point digits are calculated based on the primary or secondary number of the address. The USPS publishes the rules for calculating the delivery point in a document called the CASS Technical Guide.[18]

Structure and allocation

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ZIP Codes designatedelivery pointswithin the United States (and its territories).

Types

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There are four types of ZIP Codes:

  • Unique: assigned to a single high-volume address
  • Post office box-only: used only for PO boxes at a given facility, not for any other type of delivery
  • Military: used to route mail for the U.S. military
  • Standard: all other ZIP Codes.

Unique ZIP Codes are used for governmental agencies, universities, businesses, or buildings receiving sufficiently high volumes of mail to justify the assignment to them of exclusive ZIP Codes. Government examples include 20505 for theCentral Intelligence Agencyin Washington, D.C., and 81009 for theFederal Citizen Information Centerof theU.S. General Services Administration(GSA)[19]inPueblo, Colorado.An example of a university-specific ZIP Code is 21252, which servesTowson University.An example of a private address unique ZIP Code is that assigned to the headquarters ofWalmart(72716). They may also be assigned to a single program, such as the Postal Service'sOperation Santa Clausprogram, under which children are invited to write to Santa Claus at "North Pole 88888".[20]

An example of a PO box-only ZIP Code is 22313, used for boxes at the main post office inAlexandria, Virginia,including those used by theUnited States Patent and Trademark Office.In the area surrounding that post office, home and business mail delivery addresses use ZIP Code 22314, a standard ZIP Code.

Geographic hierarchy

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Primary state prefixes

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ZIP Code zones in the United States

ZIP Codes are numbered with the first digit representing a certain group of U.S. states, the second and third digits together representing aregionin that group (or perhaps a large city) and the fourth and fifth digits representing a group of delivery addresses within that region. The main town in a region (if applicable) often gets the first ZIP Codes for that region; afterward, the numerical order often follows the alphabetical order.[citation needed]Because ZIP Codes are intended for efficient postal delivery, there are unusual cases where a ZIP Code crosses state boundaries, such as a military facility spanning multiple states or remote areas of one state most easily serviced from a bordering state. For example, ZIP Code 42223 servesFort Campbell,which spansChristian County, Kentucky,andMontgomery County, Tennessee,and ZIP Code 97635 includes portions ofLake County, Oregon,andModoc County, California.

In general, the first three digits designate asectional center facility,the mail sorting and distribution center for an area. A sectional center facility may have more than one three-digit code assigned to it. For example, the Northern Virginia sectional center facility inMerrifieldis assigned codes 220, 221, 222, and 223. In some cases, a sectional center facility may serve an area in an adjacent state, usually due to the lack of a proper location for a center in that region. For example, 739 in Oklahoma is assigned toAmarillo, Texas;297 inSouth Carolinais assigned toCharlotte, North Carolina;865 in Arizona is assigned toAlbuquerque, New Mexico;and 961 inCaliforniatoReno, Nevada.

Many of the lowest ZIP Codes, which begin with '0', are in theNew Englandregion. In the '0' region are New Jersey (non-contiguous with the remainder of the '0' area),Puerto Rico,theU.S. Virgin Islands,andAPO/FPOmilitary addresses for personnel stationed in Europe, Africa, Southwest Asia, and onboard vessels based in the waters adjoining those lands. The lowest ZIP Code is inHoltsville, New York(00501, a ZIP Code exclusively for theU.S. Internal Revenue Servicecenter there).[21]Other low ZIP Codes are 00601 forAdjuntas, Puerto Rico;01001 forAgawam, Massachusetts,and the ZIP Codes 01002 and 01003 forAmherst, Massachusetts;01002 is used for mail in town, while 01003 is reserved for theUniversity of Massachusetts Amherst.Until 2001, there were six ZIP Codes lower than 00501 that were numbered from 00210 to 00215 (located inPortsmouth, New Hampshire) and were used by theDiversity Immigrant Visaprogram to receive applications from non-U.S. citizens.[citation needed]

The numbers increase southward along theEast Coast,such as 02115 (Boston), 10001 (New York City), 19103 (Philadelphia), 21201 (Baltimore), 20008 (Washington, D.C.), 30303 (Atlanta), and 33130 (Miami) (these are only examples, as each of these cities contains several ZIP Codes in the same range). From there, the numbers increase heading westward and northward east of theMississippi River,southward west of the Mississippi River, and northward on theWest Coast.For example, 40202 is inLouisville,50309 inDes Moines,60601 inChicago,63101 inSt. Louis,77036 inHouston,80202 inDenver,94111 inSan Francisco,98101 inSeattle,and 99950 inKetchikan, Alaska(the highest ZIP Code).

The first digit of the ZIP Code is allocated as follows:

Secondary regional prefixes (123xx) and local ZIP Codes (12345)

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Early advertisement for ZIP Code 10005

The second and third digits represent thesectional center facility(SCF) (e.g. 477xx =Vanderburgh County, Indiana), and the fourth and fifth digits represent the area of the city (if in ametropolitan area), or a village/town (outside metro areas), e.g. 47722 (4=Indiana, 77=Vanderburgh County, 22=University of Evansvillearea). When a sectional center facility's area crosses state lines, that facility is assigned separate three-digit prefixes for the states that it serves.

In some urban areas, like 462 forMarion County, Indiana,the three-digit prefix will often exist in one county, while, in rural and most suburban areas, the prefix will exist in multiple counties; for example, the neighboring 476 prefix is found in part or entirely in six counties: Gibson, Pike, Posey, Spencer, Vanderburgh, and Warrick. In some cases, an urban county may have more than one prefix. This is the case with Allen (467, 468), Lake (464, 463), St. Joseph (465, 466), and Vanderburgh (476, 477) counties. Cities likeChicago,Houston,Los Angeles,andNew York Cityhave multiple prefixes within their city limits. In some cases, these may be served from the same SCF, such as inSan Diego County, California,where the three-digit prefixes 919 and 920 are used for suburban and rural communities, and 921 for the city of San Diego itself, although all three are processed through the same SCF.[citation needed]

Despite the geographic derivation of most ZIP Codes, the codes themselves do not represent geographic regions; in general, they correspond to address groups or delivery routes. As a consequence, ZIP Code "areas" can overlap, be subsets of each other, or be artificial constructs with no geographic area (such as 095 for mail to the Navy, which is not geographically fixed). In similar fashion, in areas without regular postal routes (rural routeareas) or no mail delivery (undeveloped areas), ZIP Codes are not assigned or are based on sparse delivery routes, and hence the boundary between ZIP Code areas is undefined. For example, some residents in or nearHaubstadt, Indiana,which has the ZIP Code 47639, have mailing addresses with 47648, the ZIP Code for neighboringFort Branch, Indiana,while others living in or near Fort Branch have addresses with 47639. Many rural counties have similar logistical inconsistencies caused by the aforementioned sparse delivery routes, often known as Rural Routes or by some other similar designation.

International mail

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There are generally no ZIP Codes for deliveries to other countries, except for the independent countries of theFederated States of Micronesia,theRepublic of the Marshall Islands,and theRepublic of Palau,each of which is integrated into the U.S. postal system under aCompact of Free Association.[22]Another exception is ZIP Codes used for overseas stations of U.S. armed forces.[23]

Mail toU.S. diplomatic missionsoverseas is addressed as if it were addressed to a street address inWashington, D.C.The four-digitdiplomatic pouchnumber is used as a building number, while the city in which the embassy or consulate is located is combined with the word "Place" to form a fictional street name. Each mission uses a ZIP+4 Code consisting of20521and the diplomatic pouch number.[citation needed]

For example, theU.S. Embassy in Indiahas this address in India's postal system:[24]

Embassy of the United States of America
Shantipath, Chanakyapuri,
New Delhi,
National Capital Territory of Delhi,110021

as well as this U.S. address:[25]

Embassy of the United States of America
9000 New Delhi Place
Washington, DC20521-9000

Individuals posted at diplomatic missions overseas are now assigned a Diplomatic Post Office address and unique box number. The ZIP Code identifies the diplomatic mission destination and is different from the diplomatic pouch number in the example above. While delivered through the pouch system, mail to such addresses are not considered "Diplomatic Pouch" materials, and as such must adhere to the mailing regulations of the host country. An example address is:[26]

JOHN ADAMS
UNIT 8400 BOX 0000
DPO AE09498-0048

Division and reallocation

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Likearea codes,ZIP Codes are sometimes divided and changed, especially when aruralarea becomessuburban.Typically, the new codes become effective once announced, and a grace period (e.g., one year) is provided in which the new and old codes are used concurrently so that postal patrons in the affected area can notify correspondents, order new stationery, etc.[27]

In rapidly growing communities, it is sometimes necessary to open a new sectional center facility, which must then be allocated its own three-digit ZIP-code prefix or prefixes. Such allocation can be done in various ways. For example, when a new sectional center facility was opened atDulles Airportin Virginia, the prefix 201 was allocated to that facility; therefore, for all post offices to be served by that sectional center facility the ZIP Code changed from an old code beginning with 220 or 221 to a new code or codes beginning with 201. However, when a new sectional center facility was opened to serveMontgomery County, Maryland,no new prefix was assigned. Instead, ZIP Codes in the 207 and 208 ranges, which had previously been assigned alphabetically, were reshuffled so that 207xx ZIP Codes in the county was changed to 208xx codes, while 208xx codes outside that county were changed to 207xx codes. BecauseSilver Spring(whose postal area includesWheaton) has its own prefix, 209, there was no need to apply the reshuffling to Silver Spring; instead, all mail going to 209xx ZIP Codes was simply rerouted to the new sectional center facility.

On the other hand,depopulationmay cause a post office to close and its associated ZIP Code to be deallocated. For example,Centralia, Pennsylvania's ZIP Code, 17927, was retired in 2002,[28]and ZIP Codes forOnoville(14764),Quaker Bridge(14771) andRed House(14773) in New York were prevented from going into use in 1964 in preparation for theKinzua Dam's completion.[29][30]

Relationship with local government boundaries

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Each ZIP Code has one or more "postal city" names assigned to it. Since ZIP Code boundaries are based on the areas served by each physical post office, they often do not coincide with the boundaries of local government units. For example, suburban andunincorporated areasmay share a postal city name with a neighboring municipality, even if no part of its ZIP Code is actually within that city.[31]

Other uses

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Delivery services

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Delivery services other than the USPS, such asFedEx,United Parcel Service,andDHL,require a ZIP Code for optimal internal routing of a package.[32]

Statistics

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As of October 2019,there are 41,702 ZIP Codes in the United States.[33]Due to convenience, ZIP Codes are used not only for tracking of mail, but also commonly for gathering geographical statistics in the United States by some researchers.[34][35]ZIP Codes are not created for statistical analysis, thus use for statistical analysis is heavily criticized for numerous reasons and advised against as a cartographic practice.[35][36]As ZIP Codes are not polygons, but collections of mail routes and points, they are unsuitable for publication or distribution of most data.[37]Polygons for ZIP Codes are not released by the USPS and instead interpolated by 3rd party vendors.[34]These interpolations introduce topological errors and are not standard between vendors.[34]The USPS often discontinues, splits, or otherwise modifies ZIP Codes, making continuous space-time analysis challenging, leading to issues with both themodifiable areal unit problem(MAUP) andmodifiable temporal unit problem(MTUP).[34][36]As the ZIP Codes are postal routing numbers, individuals and organizations without concrete spatial locations may be given their own number, making it impossible to associate demographic data with them.[34]Demographic data is not consistent between ZIP Codes, and no effort is made to ensure they are proper enumeration units for analysis.[34]As ZIP Codes are not made with the same considerations as other enumeration units, and is not possible without committing theecological fallacy.[34][35]This again becomes an issue with the MAUP. They have been found not to have significant correlations with health indicators, which can lead to poor conclusions.[35]Despite these issues, ZIP Codes remain popular among researchers in fields such as public health due to their convenience, public familiarity with them, ability to anonymize subject addresses through aggregation, and possible ignorance of more appropriate enumeration units on the part of researchers.[34][36]

In an attempt to satisfy demand "by data users for statistical data by ZIP Code area", theU.S. Census Bureaucalculates approximate boundaries of ZIP Code areas, which it callsZIP Code Tabulation Areas(ZCTAs).[37][34]Statistical census data is then provided for these approximate areas. The geographic data provided for these areas includes thelatitudeandlongitudeof the center-point of the ZCTAs. ZIP Codes are inherently discrete orpoint-baseddata, as they are assigned only at the point of delivery, not for the spaces in between the delivery points. The United States Census Bureau then interpolates this discrete data set to create polygons by attempting to match ZIP Code extents with Census blocks.[34]The resulting aerial units represent the approximate extent of the ZIP Code which are combined with to use for mapping and data presentation. The process of creating ZCTAs and their use for statistical analysis are heavily criticized in the literature. First, the creation of ZCTAs from Census blocks encounters issues when a Census block straddles multiple ZIP Codes.[34]Addressing this is another instance of the MAUP, and the solution of dividing aggregate units between ZIP Codes causes some individuals to fall into ZCTAs that do not match their ZIP Code.[34]The creation of these units is therefore committing theecological fallacyby attempting to disaggregate aggregate data. As ZIP Codes are not continuous, not everyone in the United States has one, and there are ZIP Codes for non-populated or geographic areas, resulting in there not being one ZCTA for every ZIP Code.[34]ZCTAs are not updated as frequently as the USPS updates ZIP Codes, resulting in further temporal analysis issues when ZIP Codes change during a study period.[34]Datasets providing a similar approximate geographic extent to ZCTA are commercially available. Despite these issues, ZCTAs are still very popular with researchers in fields like epidemiology, and among government agencies, with some states employing them to publish and distribute public health data during the COVID-19 pandemic.[36]

Marketing

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The data is often used indirect mail marketingcampaigns in a process called ZIP-code marketing.Point-of-salecashiers sometimes ask consumers for their home ZIP Codes. Besides providing purchasing-pattern data useful in determining the location of new business establishments, retailers can use directories to correlate this ZIP Code with the name on a credit card to obtain a consumer's full address andtelephone number.ZIP-Coded data are also used in analyzing geographic factors in risk, an insurance and banking industry practice pejoratively known asredlining.This can cause problems,e.g.,expensive insurance, for people living near a town with a high crime rate and sharing its ZIP Code, while they live in a relatively crime-free town. (See Elkins Park, Pennsylvania, above.)

California outlawed this practice in 2011.[38]

Legislative districts

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ZIP Codes may not currently be used to identify existing legislative districts. Although the website of theUnited States House of Representativeshas a "Find Your Representative" feature that looks up congressional districts based on ZIP Codes alone, it often returns multiple districts corresponding to a single ZIP Code.[39][40]This is because different parts of one ZIP Code can be in different districts.[41]One proposal to eliminate the possibility of extreme partisangerrymanderingcalls on using ZIP Codes as the basic units for redistricting.[42]

Internet

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A 1978 proposal for a nationwide system of community networks suggested using ZIP Codes forrouting.[43]

ZIP Code data is an integral part of dealer /store locatorsoftware on manywebsites,especiallybrick-and-clickwebsites. This software processes a user-input ZIP Code and returns a list of store or business locations, usually in the order of increasing distance from the center of the input ZIP Code. As the ZIP Code system is confined to the U.S. Postal network, websites that require ZIP Codes cannot register customers outside the United States. Many sites will purchase postal code data of other countries or make allowances in cases where the ZIP Code is not recognized.[citation needed]

ZIP Codes are regularly used on the Internet to provide a location in situations where an exact address is not necessary (or desirable) but the user's municipality or general location is needed. Examples (in addition to the store locator example listed above) include weather forecasts, television listings, local news, andonline dating(most general-purpose sites, by default, search within a specifiedradiusof a given ZIP Code, based on other users' entered ZIP Codes).

Credit card security

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ZIP Codes are used in credit card authorization, specificallyAddress Verification System(AVS). When a merchant collects the entire address, the ZIP Code is an important part of AVS. In some cases, the ZIP Code is the only thing used for AVS, specifically where collecting a signature, or other information is infeasible, such aspay at the pumporvending machines.[citation needed]

See also

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References

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  1. ^Curtin, Abby."Flashing Across the Country: Mr. Zip and the ZIP Code Promotional Campaign".Smithsonian National Postal Museum.Archivedfrom the original on May 30, 2023.RetrievedMay 30,2023.
  2. ^"The Untold Story of the ZIP Code"(PDF).U.S. Postal Service Office of Inspector General.April 1, 2013. Archived fromthe original(PDF)on December 29, 2016.RetrievedMarch 11,2020.When Day unveiled the nationwide 5-digit ZIP Code at a postmasters' convention in October of 1962, he simultaneously introduced the world to "Mr. ZIP" — the cartoon character whose body language symbolizes speedy delivery.
  3. ^Terrell, Ellen (June 28, 2013)."This Month in Business History: ZIP Code Introduced".Library of Congress Research Guides.Archivedfrom the original on October 29, 2021.RetrievedJuly 31,2022.
  4. ^"Latest Status Info".United States Patent and Trademark Office.Archivedfrom the original on June 30, 2012.RetrievedDecember 22,2019.
  5. ^"A Zoning System in Development".Smithsonian National Postal Museum. Archived fromthe originalon January 4, 2012.RetrievedDecember 22,2019.
  6. ^"Home Folks to Have P.O. Numbers Like Army Boys".Minneapolis Morning Tribune. May 6, 1943.Archivedfrom the original on February 1, 2023.RetrievedJanuary 31,2023.
  7. ^abChokshi, Niraj (April 23, 2013)."The Bounty ZIP Codes Brought America".The Atlantic.Archivedfrom the original on October 26, 2020.RetrievedMarch 12,2020....Postmaster General Edward Day in the early 1960s suggested combining Moon's three-digit code with the existing two-digit system.
  8. ^abcd"State Abbreviations", USPS.comArchived2017-01-16 at theWayback Machine.
  9. ^Bullamore, Tim (2001). Robert Moon Obituary. Retrieved fromhttps://www.independent.co.uk/news/obituaries/robert-moon-729034.html[dead link].
  10. ^Martin, Douglas (April 14, 2001)."Robert Moon, an Inventor of the ZIP Code, Dies at 83".New York Times.Archivedfrom the original on February 17, 2020.RetrievedSeptember 23,2017.
  11. ^abKelly, John (September 29, 2018)."Virginia resident pushed the envelope when Zip code was born in 1963".The Washington Post.Archivedfrom the original on October 10, 2018.RetrievedAugust 13,2022.
  12. ^"Papers of H. Bentley Hahn: The Man Who Invented the 5-Digit ZIP Code – ARCHIVALLY SPEAKING: An Inside Look at the JFK Library Archives".archiveblog.jfklibrary.org.Archived fromthe originalon May 1, 2018.RetrievedApril 30,2018.
  13. ^ab"Mr. ZIP- The nation's original 'digital' icon"(PDF).Archived fromthe original(PDF)on May 8, 2009.
  14. ^"The US Postal Service's zip code system turns 50".Southern California Public Radio.July 1, 2013.Archivedfrom the original on June 16, 2020.RetrievedJune 16,2020.
  15. ^"Organizing America: A History of the ZIP Code".RandomHistory.com.Random History. July 25, 2014. Archived fromthe originalon August 12, 2014.RetrievedJune 19,2017.
  16. ^"ZIP Code™ Lookup | USPS".tools.usps.com.Archivedfrom the original on December 22, 2016.RetrievedJanuary 23,2020.
  17. ^"Archived: How can I print routing barcodes on envelopes? – Knowledge Base".The Trustees of Indiana University.Archivedfrom the original on March 10, 2012.RetrievedJuly 10,2009.
  18. ^"CASS Technical Guide"(PDF).United States Postal Service. p. 40. Archived fromthe original(PDF)on April 19, 2009.RetrievedJuly 10,2009.
  19. ^"FCIC – About Us".Federal Citizen Information Center of the U.S. General Services Administration. Archived fromthe originalon July 14, 2009.RetrievedJuly 10,2009.For years, consumers have written to Pueblo, Colorado 81009 for timely, practical information they trust.
  20. ^Miller, Susan."'Don't forget about me': USPS' Operation Santa looking for donors to make magic this year ".USA TODAY.Archivedfrom the original on November 24, 2022.RetrievedDecember 2,2022.
  21. ^"USPS Postal Facts".facts.usps.com. February 15, 2018. Archived fromthe originalon August 19, 2018.RetrievedMay 31,2018.
  22. ^"Freely Associated States".www.doi.gov.July 24, 2019.Archivedfrom the original on May 20, 2022.RetrievedApril 20,2022.
  23. ^"Military Addresses".United States Postal Service.Archivedfrom the original on December 15, 2018.RetrievedDecember 15,2018.
  24. ^"U.S. Embassy and Consulates in India".Archivedfrom the original on January 28, 2022.RetrievedSeptember 23,2022.
  25. ^"Mail Management".Diplomatic Pouch and Mail Division of the U.S. Department of State.Archivedfrom the original on June 30, 2019.RetrievedApril 1,2015.
  26. ^"Military & Diplomatic Mail | USPS".www.usps.com.Archived fromthe originalon August 19, 2019.RetrievedAugust 8,2019.
  27. ^Roberts, Sam (March 21, 2007)."An Elite ZIP Code Becomes Harder to Crack".The New York Times.p. C15.Archivedfrom the original on January 26, 2021.RetrievedJuly 10,2009.
  28. ^Wheary, Rob."Centralia loses its ZIP".Archived fromthe originalon March 24, 2012.RetrievedMay 2,2010.
  29. ^"Post Offices to Close".The Bradford Era.April 22, 1964.
  30. ^"Final Check-Out".Salamanca Republican-Press.July 1, 1964.
  31. ^Stevens, Nye (June 23, 2006)."Changing Postal ZIP Code Boundaries"(PDF).Congressional Research Service. p. 2.RetrievedSeptember 9,2024.
  32. ^"USPS.com FAQs".faq.usps.com.Archived fromthe originalon February 22, 2019.RetrievedFebruary 21,2019.
  33. ^"ZIP Codes".Archived fromthe originalon October 19, 2019.
  34. ^abcdefghijklmnGrubesic, Tony H; Matisziw, Timothy C (2006)."On the use of ZIP codes and ZIP code tabulation areas (ZCTAs) for the spatial analysis of epidemiological data".International Journal of Health Geographics.58(5): 58.doi:10.1186/1476-072X-5-58.PMC1762013.PMID17166283.
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