Editing ZIP Code (section)

===Geographic hierarchy===

====Primary state prefixes====
[[File:ZIP Code zones.svg|thumb|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 a [[region]] in 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|date=April 2010}} 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 serves [[Fort Campbell]], which spans [[Christian County, Kentucky]], and [[Montgomery County, Tennessee]], and ZIP Code 97635 includes portions of [[Lake County, Oregon]], and [[Modoc County, California]].

The first three digits generally designate a [[sectional center facility]], the area's mail sorting and distribution center. A sectional center facility may have more than one three-digit code assigned to it. For example, the Northern Virginia sectional center facility in [[Merrifield, Virginia|Merrifield]] is 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 to [[Amarillo, Texas]]; 297 in [[South Carolina]] is assigned to [[Charlotte, North Carolina]]; 865 in Arizona is assigned to [[Albuquerque, New Mexico]]; and 961 in [[California]] to [[Reno, Nevada]].

Many of the lowest ZIP Codes, which begin with&nbsp;'0', are in the [[New England]] region. In the '0' region are New Jersey (non-contiguous with the remainder of the '0' area), [[Puerto Rico]], the [[U.S. Virgin Islands]], and [[APO/FPO]] military addresses for personnel stationed in Europe, Africa, Southwest Asia, and onboard vessels based in the waters adjoining those lands. The lowest ZIP Code is in [[Holtsville, New York]] (00501, a ZIP Code exclusively for the U.S. [[Internal Revenue Service]] center there).<ref>{{cite web |url=https://facts.usps.com/map/#fact147 |title=USPS Postal Facts |publisher=facts.usps.com |date=2018-02-15 |access-date=2018-05-31 |archive-url=https://web.archive.org/web/20180819070643/https://facts.usps.com/map/#fact147 |archive-date=2018-08-19 |url-status=dead }}</ref> Other low ZIP Codes are 00601 for [[Adjuntas, Puerto Rico]]; 01001 for [[Agawam, Massachusetts]], and the ZIP Codes 01002 and 01003 for [[Amherst, Massachusetts]]; 01002 is used for mail in town, while 01003 is reserved for the [[University of Massachusetts Amherst]]. Until 2001, there were six ZIP Codes lower than 00501 that were numbered from 00210 to 00215 (located in [[Portsmouth, New Hampshire]]) and were used by the [[Diversity Immigrant Visa]] program to receive applications from non-U.S. citizens.{{citation needed|date=April 2010}}

The numbers increase southward along the [[East Coast of the United States|East 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 the [[Mississippi River]], southward west of the Mississippi River, and northward on the [[West Coast of the United States|West Coast]]. For example, 40202 is in [[Louisville, Kentucky|Louisville]], 50309 in [[Des Moines, Iowa|Des Moines]], 60601 in [[Chicago]], 63101 in [[St. Louis]], 77036 in [[Houston]], 80202 in [[Denver]], 94111 in [[San Francisco]], 98101 in [[Seattle]], and 99950 in [[Ketchikan, Alaska]] (the highest ZIP Code).

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

* 0 = [[Connecticut]] (CT), [[Massachusetts]] (MA), [[Maine]] (ME), [[New Hampshire]] (NH), [[New Jersey]] (NJ), [[New York (state)|New York]] (NY, [[Fishers Island, New York|Fishers Island only]]), [[Puerto Rico]] (PR), [[Rhode Island]] (RI), [[Vermont]] (VT), [[Virgin Islands]] (VI), Army Post Office Europe, Central Asia, and the Middle East (APO AE); Fleet Post Office Europe and the Middle East (FPO AE)
* 1 = [[Delaware]] (DE), [[New York (state)|New York]] (NY), [[Pennsylvania]] (PA)
* 2 = [[District of Columbia]] (DC), [[Maryland]] (MD), [[North Carolina]] (NC), [[South Carolina]] (SC), [[Virginia]] (VA), [[West Virginia]] (WV)
* 3 = [[Alabama]] (AL), [[Florida]] (FL), [[Georgia (U.S. state)|Georgia]] (GA), [[Mississippi]] (MS), [[Tennessee]] (TN), Army Post Office Americas (APO AA), Fleet Post Office Americas (FPO AA)
* 4 = [[Indiana]] (IN), [[Kentucky]] (KY), [[Michigan]] (MI), [[Ohio]] (OH)
* 5 = [[Iowa]] (IA), [[Minnesota]] (MN), [[Montana]] (MT), [[North Dakota]] (ND), [[South Dakota]] (SD), [[Wisconsin]] (WI)
* 6 = [[Illinois]] (IL), [[Kansas]] (KS), [[Missouri]] (MO), [[Nebraska]] (NE)
* 7 = [[Arkansas]] (AR), [[Louisiana]] (LA), [[Oklahoma]] (OK), [[Texas]] (TX)
* 8 = [[Arizona]] (AZ), [[Colorado]] (CO), [[Idaho]] (ID), [[New Mexico]] (NM), [[Nevada]] (NV), [[Utah]] (UT), [[Wyoming]] (WY)
* 9 = [[Alaska]] (AK), [[American Samoa]] (AS), [[California]] (CA), [[Guam]] (GU), [[Hawaii]] (HI), [[Marshall Islands]] (MH), [[Federated States of Micronesia]] (FM), [[Northern Mariana Islands]] (MP), [[Oregon]] (OR), [[Palau]] (PW), [[Washington (state)|Washington]] (WA), Army Post Office Pacific (APO AP), Fleet Post Office Pacific (FPO AP)

====Secondary regional prefixes (123xx) and local ZIP Codes (12345)====
{{See also|List of ZIP Code prefixes}}
[[File:10005 zip code.jpg|thumb|Early advertisement for ZIP Code 10005]]

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

In some urban areas, like 462 for [[Marion 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 like [[Chicago]], [[Houston]], [[Los Angeles]], and [[New York City]] have multiple prefixes within their city limits. In some cases, these may be served from the same SCF, such as in [[San 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|date=December 2007}}

Despite the geographic derivation of most ZIP Codes, the codes do not represent geographic regions; generally, they correspond to address groups or delivery routes. Consequently, 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). Similarly, in areas without regular postal routes ([[Rural delivery service|rural route]] areas) 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 near [[Haubstadt, Indiana]], which has the ZIP Code 47639, have mailing addresses with 47648, the ZIP Code for neighboring [[Fort Branch, Indiana]], while others living in or near Fort Branch have addresses with 47639. Many rural counties have similar logistical inconsistencies caused by the sparse delivery routes, often called Rural Routes or other similar designations.

==== International mail ====
There are generally no ZIP Codes for deliveries to other countries, except for the independent countries of the [[Federated States of Micronesia]], the [[Republic of the Marshall Islands]], and the [[Republic of Palau]], each of which is integrated into the U.S. postal system under a [[Compact of Free Association]].<ref>{{Cite web |date=2019-07-24 |title=Freely Associated States |url=https://www.doi.gov/ocl/freely-associated-states |url-status=live |archive-url=https://web.archive.org/web/20220520215245/https://www.doi.gov/ocl/freely-associated-states |archive-date=May 20, 2022 |access-date=2022-04-20 |website=www.doi.gov |language=en}}</ref> Another exception is ZIP Codes used for overseas stations of U.S. armed forces.<ref>{{cite web |title=Military Addresses |url=https://pe.usps.com/text/pub28/28c2_010.htm |url-status=live |archive-url=https://web.archive.org/web/20181215222409/https://pe.usps.com/text/pub28/28c2_010.htm |archive-date=December 15, 2018 |access-date=December 15, 2018 |publisher=[[United States Postal Service]]}}</ref>

Mail to [[List of diplomatic missions of the United States|U.S. diplomatic missions]] overseas is addressed as if it were addressed to a street address in [[Washington, D.C.]] The four-digit [[diplomatic pouch]] number 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 of '''20521''' and the diplomatic pouch number.{{Citation needed|date=April 2022}}

For example, the [[Embassy of the United States, New Delhi|U.S. Embassy in India]] has this address in India's postal system:<ref>{{cite web |title=U.S. Embassy and Consulates in India |url=https://in.usembassy.gov/ |url-status=live |archive-url=https://web.archive.org/web/20220128174246/https://in.usembassy.gov/ |archive-date=January 28, 2022 |access-date=September 23, 2022}}</ref>

<blockquote>
<poem>
Embassy of the United States of America
Shantipath, Chanakyapuri,
New Delhi,
National Capital Territory of Delhi, [[Postal Index Number|110021]]
</poem>
</blockquote>

as well as this U.S. address:<ref>{{cite web |title=Mail Management |url=https://2009-2017.state.gov/m/a/c8028.htm |url-status=live |archive-url=https://web.archive.org/web/20190630191152/https://2009-2017.state.gov/m/a/c8028.htm |archive-date=June 30, 2019 |access-date=April 1, 2015 |publisher=Diplomatic Pouch and Mail Division of the U.S. Department of State}}</ref>

<blockquote>
<poem>
Embassy of the United States of America
9000 New Delhi Place
Washington, DC{{nbsp}}{{nbsp}}20521-9000
</poem>
</blockquote>

Individuals posted at diplomatic missions overseas are now assigned a Diplomatic Post Office address and a unique box number. The ZIP Code identifies the diplomatic mission destination and differs from the diplomatic pouch number in the example above. While delivered through the pouch system, mail to such addresses is not considered "Diplomatic Pouch" material and must adhere to the mailing regulations of the host country. An example address is:<ref>{{cite web |title=Military & Diplomatic Mail {{!}} USPS |url=https://www.usps.com/ship/apo-fpo-dpo.htm |url-status=dead |archive-url=https://web.archive.org/web/20190819001108/https://www.usps.com/ship/apo-fpo-dpo.htm |archive-date=19 August 2019 |access-date=8 August 2019 |website=www.usps.com}}</ref>

<blockquote>
<poem>
JOHN ADAMS
UNIT 8400 BOX 0000
DPO AE{{nbsp}}{{nbsp}}09498-0048
</poem>
</blockquote>