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When you download our U.S. or Canadian Postal CodeOM databases, you can choose between 4 separate formats for download, saving on conversion time and effort. Our zip codes database has the most comprehensive and precise data that you will find. You can perform free database lookups on our website with our software or you can download our ZIP codes database for data manipulation. Our free ZIP codes finder helps you find the ZIP codes and related demographic information for any U.S. or Canadian Postal CodeOM.
ZIP Code & Postal Code Facts
Zip Codes are largely responsible for the automation of the United States Post Office’s mail handling. Today, over 600,000,000 pieces of mail are delivered each business day, and our mail can take as little as one day to reach its destination. Back in 1799, it could take three weeks for a letter to travel from Lexington, Massachusetts to Philadelphia, Pennsylvania. The cost of mail was relatively much higher back then. It cost twenty-five cents to send a letter 450 miles – not much less than it costs today to send a letter anywhere in the country, and in considerably less time!
Today, many of us in the United States expect to have our mail delivered to our homes and offices at no extra charge. Before July 1, 1863, city residents had to pay to have a postal worker bring their mail to them; rural customers had to travel to pick up their own mail for another 30 years. Zip codes wouldn't have helped much in those days.
Many famous Americans have been postal workers. Benjamin Franklin is known as “The Father of the United States Postal Service.” Abraham Lincoln was postmaster of New Salem, Illinois in the 1830’s, and it is rumored that he personally delivered mail by carrying it in his hat along with a list of delivery places. Harry S. Truman was postmaster of Grandview, Missouri for a time. William Faulkner was postmaster of the University of Mississippi Post Office.
Perhaps the most romantic era in our United States postal history is that of the Pony Express. Before then, stagecoaches took more than 20 days to deliver mail from coast to coast. In 1860, William H. Russell bought strong horses and put a listing for good horseback riders in newspaper ads that read: “Wanted: Young, skinny, wiry fellows not over 18. Must be expert riders willing to risk death daily. Orphans preferred.” Russell’s Pony Express was in service for 18 months, cutting the time it took for mail delivery coast to coast in half. The service closed in 1861 when telegraph lines connecting the coasts were finished being laid, allowing people to send information much faster and cheaper than they could by Pony Express.
The history of the United States Post Office is filled with fascinating data and amusing facts. Did you know the first Post Office in the United States was actually a tavern? Or that the United States employed camels to deliver mail over deserts in the Southwest? Or that one of the first airmail deliveries involved a three mile flight, and that the pilot dropped the bag of mail from the flying plane to a postmaster waiting below?
Zip Codes didn’t come into use until 1963. Their inventor, Robert Aurand Moon, is known as the “Father of ZIP Codes” and was nicknamed “Mr. ZIP Code.” Another character also went by this name: the lovable cartoon ambassador, Mr. Zip or Mr. Zippy, who some think was largely responsible for the success of United States ZIP code compliance.
And just what are ZIP Codes? And how does the United States Post Office use them? What do the numbers stand for? Where does the ZIP code data come from? How about the ZIP + 4 Codes? There’s plenty to learn about the Zoning Improvement Plan Codes!
To learn more about our ZIP Code finder - US ZIP Code Database Lists with Demographics Information, please view our FAQ's.
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About US ZIP Codes
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US ZIP codes are a type of postal code used within the United States to help the United States Postal Service (USPS) route mail more efficiently. ZIP codes near me are shown on the map above. Some still refer to ZIP codes as US postal codes. The term ZIP stands for Zone Improvement Plan. The basic 5-digit format was first introduced in 1963 and later extended to add an additional 4 digits after a dash to form a ZIP+4 code. The additional 4 digits help USPS more precisely group mail for delivery. Though ZIP codes were originally developed for USPS, many other shipping companies such as United Parcel Service (UPS), Federal Express (FedEx), DHL, and others make use of ZIP codes for sorting packages and calculating the time and cost of shipping a package (the shipping rate).
Types of Zip Codes
- Unique/single high volume address (ex. 20505 for the CIA in Washington, DC)
- PO Box only (ex. 22313 for the PO Boxes of Alexandria, VA)
- Military
- Standard (all other ZIP codes)
Assignment of ZIP codes and Mail Sorting
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The first digit of a USA ZIP code generally represents a group of U.S. states. 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).
The ZIP+4 code is not required, but it aids the post office in additional sorting of mail. A ZIP+4 code may correspond to a city block, group of apartments, or an individual high-volume receiver. It is also common for each PO Box number to correspond to a unique ZIP+4 code. Sometimes, several PO Box numbers are grouped into the same ZIP+4 code by using the last several digits of the PO Box number. This method isn't a universal rule though so the ZIP+4 must still be looked up for each PO Box.
Places in the US so Remote, They Don't Have a ZIP
As you can see from the map, not everywhere in the US is assigned a ZIP code. Remote and especially rural areas of the country do not have enough deliverable addresses to create a mail route. Without mail delivery, a ZIP is not needed. If you are looking to get off the grid, these areas are some of the most remote places within the country.USA ZIP Code Boundaries
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. For instance, a single ZIP code is used for all US Navy mail. 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.
US ZIP Code Map
No official ZIP code map according to actual USPS data exists. 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.
On this site, all ZIP code maps use the ZIP Code Tabulation Areas (ZCTAs) as specified by the United States Census Bureau in 2010 (or newer) and discussed below. 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. Very rural areas aren't labeled as belonging to a ZIP code (such as much of Nevada and Utah) where there are few, if any, addresses to deliver mail. If the address is on the same street as a ZIP code boundary on the map, be sure to search for the full street address to determine the ZIP code instead of relying on the map.
ZIP Code Tabulation Areas (ZCTAs)
ZIP code tabulation areas were developed by the United States Census Bureau. Their purpose is to convey statistical data about regions that are familiar to most citizens. However, ZCTAs are not exactly the same as ZIP codes. As discussed above, it is difficult to precisely define a geographic area covered by a ZIP code. ZCTAs were developed to account for some of the difficulties in assigning an area to a ZIP code and to precisely define a geographic area. Also, ZCTAs are not updated as frequently as ZIP codes. In general, they are updated once every 10 years for the Census.
The Census assigns an area to a ZCTA according to census blocks (the smallest geographic unit used by the census). Imagine a city block that makes up a typical census block as pictured to the right. It is bounded on all 4 sides by portions of city streets that each have their own name and addresses. The issue is that census blocks almost always split down the middle of the street. ZIP codes rarely do because that would require two postal workers delivering mail to that street - one for each side of the street. In the example, one mail carrier may deliver to 3 sides of the block via one ZIP code while another mail carrier delivers mail on the other street in a different ZIP code. When this happens, the Census Bureau will assign the entire block to a single ZCTA (in this case, 21044) because the census block is the area that is precisely measured. If you are getting very precise (usually a matter of meters, not miles), census block boundaries near the edge of a ZIP code almost always split ZIP codes.
The statistics provided by the Census Bureau can give insight into the demographics within the ZIP code. For instance, see our ZIP code rankings.
Matching ZIP Codes with States, Counties, and Cities
Remember that ZIP codes were made to make mail delivery easier. They weren't made to correspond to existing boundaries such as cities, counties, or even states. If it is more efficient for a mail carrier to drive across a state line to deliver mail, the ZIP code 'boundary' will cross the state lines. ZIP codes don't usually cross state lines, but some do (65733, 71749, and 73949 are good examples).
It gets even more complicated when trying to assign a ZIP code to a specific county (as much as 25% cross county lines), congressional district, metro area, time zone, area code, etc. The edges of the boundaries commonly overlap. For the purposes of our free zip code database downloads, we will commonly list either the most common region for the ZIP code or list multiple regions if several exist in the ZIP code.
For cities, the assignment is somewhat more complicated. USPS does not always use the city in which the ZIP code is located. The assignment of cities to ZIP codes is more general. The city is usually the name of the main post office. For instance, almost all ZIP codes in St. Louis County in Missouri have a city of Saint Louis when they may be more accurately described as the name of a smaller city where they are located.
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