Editing ZIP Code (section)

====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.