It's been built from the ground up using authoritative sources including the U. This means that they don't always cover a continuous geographical area. What's convenient for delivery purposes e. Since zip codes are often used for these purposes, the US Census Bureau calculates the approximate boundaries of zip code areas. These areas are called Zip Code Tabulation Areas. Some zip codes are for PO boxes only, unique to an organization, or used by the military. Such zip codes are not areas and therefore are not represented by ZCTAs.
This allows you to use the ZCTA as a proxy for additional information. The Basic free database will meet many users needs. You may want to purchase the Pro or Comprehensive versions if: You need data for infrequently-used zip codes that are unique to businesses, used for P.
You need demographic data such as age, race, education or income. You don't want to attribute your use of our data on a public-facing website. A centroid is the average position of all of the points in a shape. This is best way to convert an area into a point. For zip codes that represent discrete points, we've used authoritative sources such as the National Weather Service to geocode them into latitude and longitude.
Why don't latitude and longitude coordinates exist for some zip codes? Some zip codes, such as those used by the military, do not represent a discrete point or a ZCTA area. In these cases, it's not possible to convert a zip code to a geographical point.
Am I allowed to redistribute the database if I purchase a paid license? You are not allowed to sell the database or make it publicly available. However, you can make copies and backups of the data. You are also allowed to query the database to power publicly facing applications such as a store locator. To learn more, read the full license terms. Edit : It seems the Census has two different two-digit codings for states. I was using the first, while I should have been using the second, so the state names I listed were wrong.
I've updated the code and results with the correct list. ZipCodes are defined by a bounding box of Streets delivered to by carriers from a particular distribution center. This inexact process is the reason why the USPS does not provide spatial data. They publish relationship files that describe how their ZCTAs map to various other geographies.
The relationship files use Census geography IDs, so you'll want to grab a gazetteer file to help you convert the numeric IDs into the place or county names you're expecting. As other answers have stated, any mapping of ZIP codes to places is likely to be approximate, but I've had good luck with the Census data files. It's an approximation of it. Check out or even for a zip code that we're pruning with this added selectivity. You should be able to spot check all of these in Google Maps.
However, Google Maps is also not authoritative. In June , according to the following U. Census Bureau site there are zip codes that cross state boundries. There are ZIP Codes in more than one state. There are 9, ZIP Codes in more than one county. All states had some split sectors, with Virginia, Michigan and Ohio having an especially larger dosage. The rural route sectors, as expected, contained relatively the lion's share of split sectors.
Most of the other cases are in the lower sector range reserved for post office boxes and in Sector 99 reserved for the postmaster and business mail return. There must be some non-standard county code assignment occurring for these selected cases. We will have to further investigate these at a later date. With ArcGIS you can use the spatial join tool or in a script to find which zip code polygons intersect with more than one state polygons.
You could do a similar thing with zips and cities. You could possibly do a negative m buffer of the zips before the spatial join and see what that does. You can do a spatial intersect in PostGIS and get a list back of every State or City and the Zip Codes that they intersect, which would return multiple zip codes where multiple states intersect, and for each city that intersected the same zip, you would see that result as well.
So the list you are looking for should be the same as in previous answers, such as this one. The map of the first digit of zip codes above shows they are assigned in order from the north east to the west coast.
The first 3 digits of a ZIP code determine the central mail processing facility, also called sectional center facility or "sec center", that is used to process and sort mail.
All mail with the same first 3 digits is first delivered to the same sec center where it is sorted according to the last 2 digits and distributed to local post offices. The sec centers are not open to the public and usually do most sorting overnight. As you can see from the map of the first 3 digits of zip codes , the digits after the first are also generally assigned from east to west. In the map, 0 is closer to white and 9 is much more vivid. It's easy to follow the gradient across each of the zones even though there are a few exceptions such as the southwest tip of Georgia which uses 39XXX like central Mississippi.
Despite the fact that ZIP codes seem to be geographic in nature, that wasn't their intended purpose. They are intended to group mail to allow the USPS to deliver mail more efficiently. Some ZIP codes will span multiple states in order to make mail routing and delivery more efficient. In most cases, addresses in close proximity to each other are grouped in the same ZIP code which gives the appearance that ZIP codes are defined by a clear geographic boundary.
However, some ZIP codes have nothing to do with geogaphic areas. When ZIP codes appear to be geographically grouped, a clear shape cannot always be drawn around the ZIP code because ZIP codes are only assigned to a point of delivery and not the spaces between delivery points. In areas without a regular postal route or no mail delivery, ZIP codes may not be defined or have unclear boundaries. The main issue is discussed above: there simply isn't always a clear geographic boundary for a ZIP code.
The Census Bureau and many other commercial services will try to interpolate the data to create polygons shapes using straight lines to represent the approximate area covered by a ZIP code, but none of these maps are official or entirely accurate. They provide a very close approximation of the area covered by a ZIP code. You can easily notice some of the boundary issues when viewing our maps.
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