Editing ZIP Code (section)

====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)