# Why put Americans use state prefixes in front of zip codes? **URL:** \ **Category:** Factual Questions\ **Created:** [April 15, 2005, 4:09pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490 "2005-04-15T16:09:59Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Schnitte](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/schnitte/32/9033_2.png) [@Schnitte](https://boards.straightdope.com/u/Schnitte)\ **Post date:** [April 15, 2005, 4:09pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490/1 "2005-04-15T16:09:59Z")
It seems to me that USPS zip codes are unique throughout the United States. Yet when researching American postal addresses, I encounter frequently a two-letter state prefix put in front of the five-digit code (for example Austin TX 78711). Is this practice merely a relict from the time when there were no ZIP codes, or does it have a purpose? ---
**Author:** ![aktep](https://avatars.discourse-cdn.com/v4/letter/a/f0a364/32.png) [@aktep](https://boards.straightdope.com/u/aktep)\ **Post date:** [April 15, 2005, 4:18pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490/2 "2005-04-15T16:18:23Z")
The postal service requires city, 2-letter state code, and ZIP. They’re pretty picky, too, about which city names can be used in a particular ZIP code. Someone from the USPS will no doubt chime in on the whole reason they can’t deliver based on ZIP alone, but I understand it has to do with manual sorting (knowing which box CT goes into is easier than which box 01928 goes into), and, I’d imagine, gives the mail carrier a chance to correct your mistake if you get the ZIP wrong. ---
**Author:** ![Eonwe](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eonwe/32/240_2.png) [@Eonwe](https://boards.straightdope.com/u/Eonwe)\ **Post date:** [April 15, 2005, 4:21pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490/3 "2005-04-15T16:21:56Z")
Well, it helps in case you get one wrong. I remember in the third grade we were doing a sort of pen-pal-ish thing with a third grade class somewhere else in the US. Do to the vagueries of handwriting, they thought we were in Utah (UT) instead of Vermont (VT). The mail got to us though, due to the correct zip. Likewise I imagine that if for some reason you don’t know the zip code, or write it incorrectly, ultimately your letter will end up where it’s supposed to be if you mark the state. If I sent something to Austin TX but the zip was for Boston MA; I’m sure that the Boston PO would forward it on to the correct address in TX. ---
**Author:** ![Mehitabel](https://avatars.discourse-cdn.com/v4/letter/m/8797f3/32.png) [@Mehitabel](https://boards.straightdope.com/u/Mehitabel)\ **Post date:** [April 15, 2005, 4:24pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490/4 "2005-04-15T16:24:18Z")
Gets too confusing. There’s nine other Austins in the US besides the big one, and while a machine can figure it out with no trouble, it makes it much easier for the humans at either end to deal with the address. Some of it may be a relic, of course, but it does make sense when states can be thousands of miles apart to have an idea of what part of the country you’re talking about, especially since it’s easy for somebody to miswrite a zip code. In that case the Post Office needs to go down the hierarchy to the next piece of information: the state. This is very common. There’s ten big Springfields and tons of smaller ones in the US, which is why Matt Groenig chose that name to seem generic for this show. Now, if the person is _really_ old-fashioned they’ll use the even older multi-letter abbreviations for the states, like Calif., O., Tex., Ark… ---
**Author:** ![Kent\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kent_clark/32/105_2.png) [@Kent\_Clark](https://boards.straightdope.com/u/Kent_Clark)\ **Post date:** [April 15, 2005, 4:54pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490/5 "2005-04-15T16:54:50Z")
> [@Schnitte](#): > > It seems to me that USPS zip codes are unique throughout the United States. Yet when researching American postal addresses, I encounter frequently a two-letter state prefix put in front of the five-digit code (for example Austin TX 78711). Is this practice merely a relict from the time when there were no ZIP codes, or does it have a purpose? For all practical purposes it’s a remnant of the time before ZIP Codes. However, many people write so horribly that the sorters can’t read the Zip Code, and using the city and state gives them a second chance. ---
**Author:** ![Canadjun](https://avatars.discourse-cdn.com/v4/letter/c/76d3ee/32.png) [@Canadjun](https://boards.straightdope.com/u/Canadjun)\ **Post date:** [April 15, 2005, 5:04pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490/6 "2005-04-15T17:04:46Z")
Also applies in Canada. K1S 2P3 is unequivocally in Ottawa Ontario, but you’re still supposed to have Ottawa ON K1S 2P3 if you’re sending to someone in that postal code. ---
**Author:** ![OldGuy](https://avatars.discourse-cdn.com/v4/letter/o/3bc359/32.png) [@OldGuy](https://boards.straightdope.com/u/OldGuy)\ **Post date:** [April 15, 2005, 5:05pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490/7 "2005-04-15T17:05:30Z")
In principle if you put the 9 digit Zip code on an envelope, you shouldn’t require anything else (other than the recipient’s name if that’s important). The 9 digit ZIP indicates a single house or PO Box. I’m not positive how it works for duplexes or apartments. I’m also reminded of the story in the letter pages of Mad magazine back in the 60’s when they said a letter had been delivered to them with only a cut out picture of Alfred E. Neuman on the envelope. No on in the Post Office had even bothered to write the address on it. ---
**Author:** ![Mehitabel](https://avatars.discourse-cdn.com/v4/letter/m/8797f3/32.png) [@Mehitabel](https://boards.straightdope.com/u/Mehitabel)\ **Post date:** [April 15, 2005, 5:20pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490/8 "2005-04-15T17:20:38Z")
Actually, Germany has states too, right? (A lot fewer, I know). What’s the usual form of a letter to Germany? I’ve mailed plenty of packages there but I don’t know enough to say that I’m putting a town or state or county’s name there before the postal code. It’s usually “Mr. X., \_\_\_\_\_\_\_ stasse, Placename, Placename, postal code, Germany” I guess the first Placename is the town or city but what’s the second? ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [April 15, 2005, 5:21pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490/9 "2005-04-15T17:21:45Z")
It also helps clarify what the ZIP code numbers are if the handwriting is sloppy, as **kunilou** already pointed out. Take, for example: Adams, OR 97810 Adams, TN 37010 I have seen people’s handwriting so sloppy that those two numbers, both of which are “Adams’s zip code,” could be confused one for the other. But OR and TN should be distinguishable no matter how bad the handwriting are. ---
**Author:** ![Mehitabel](https://avatars.discourse-cdn.com/v4/letter/m/8797f3/32.png) [@Mehitabel](https://boards.straightdope.com/u/Mehitabel)\ **Post date:** [April 15, 2005, 5:24pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490/10 "2005-04-15T17:24:49Z")
…or “strasse”, even. :smack: ---
**Author:** ![Cliffy](https://avatars.discourse-cdn.com/v4/letter/c/59ef9b/32.png) [@Cliffy](https://boards.straightdope.com/u/Cliffy)\ **Post date:** [April 15, 2005, 5:33pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490/11 "2005-04-15T17:33:04Z")
Games Magazine used to run a feature where people would put puzzles on envelopes to the magazine and see if they got delivered. I always wondered whether the postal workers thought this was a neat diversion or if it just pissed them off. BTW, **Schnitte** , the state abbreviation isn’t really a prefix to the Zip Code. It’s a separate element of the address, the same way the city isn’t a prefix to the Zip either. –Cliffy ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [April 15, 2005, 5:37pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490/12 "2005-04-15T17:37:03Z")
> [@Mehitabel](#): > > Actually, Germany has states too, right? (A lot fewer, I know). What’s the usual form of a letter to Germany? I’ve mailed plenty of packages there but I don’t know enough to say that I’m putting a town or state or county’s name there before the postal code. It’s usually “Mr. X., \_\_\_\_\_\_\_ stasse, Placename, Placename, postal code, Germany” I guess the first Placename is the town or city but what’s the second? _Land_, equivalent to one of our states (or Canadian provinces). For example, Bayern is Bavaria; Niedersachsen is Lower Saxony; Schleswig-Holstein is obvious; Nordrhein-Westfalen is North Rhineland-Westphalia, and so on. So your final line would be “Munchen [i.e., Munich], Bayern, {postal code}, Germany” ---
**Author:** ![caveman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/caveman/32/7242_2.png) [@caveman](https://boards.straightdope.com/u/caveman)\ **Post date:** [April 15, 2005, 5:43pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490/13 "2005-04-15T17:43:43Z")
> [@OldGuy](#): > > In principle if you put the 9 digit Zip code on an envelope, you shouldn’t require anything else (other than the recipient’s name if that’s important). The 9 digit ZIP indicates a single house or PO Box. I’m not positive how it works for duplexes or apartments. IANAP, but in managing the (largely ZIP code dependent) database where I work, I learned that the +4 portion of the ZIP code is made of 2 numbers: the first 2, which are the sector (these are used to break a ZIP code down into areas of roughly equal population), and the last 2, which are the segment (these indicate which street, block and _usually_ side-of-street). The actual house number is still needed to get it to the right spot (although if the name is unique, that might do). ---
**Author:** ![PigBoy](https://avatars.discourse-cdn.com/v4/letter/p/97f17d/32.png) [@PigBoy](https://boards.straightdope.com/u/PigBoy)\ **Post date:** [April 15, 2005, 5:47pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490/14 "2005-04-15T17:47:23Z")
It’s not strictly necessary to use the official two letter abbreviations, is it? I frequently write out the whole state name if it’s a short one. ---
**Author:** ![GorillaMan](https://avatars.discourse-cdn.com/v4/letter/g/50afbb/32.png) [@GorillaMan](https://boards.straightdope.com/u/GorillaMan)\ **Post date:** [April 15, 2005, 5:51pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490/15 "2005-04-15T17:51:52Z")
> [@Mehitabel](#): > > Actually, Germany has states too, right? (A lot fewer, I know). What’s the usual form of a letter to Germany? I’ve mailed plenty of packages there but I don’t know enough to say that I’m putting a town or state or county’s name there before the postal code. It’s usually “Mr. X., \_\_\_\_\_\_\_ stasse, Placename, Placename, postal code, Germany” I guess the first Placename is the town or city but what’s the second? Don’t know about Germany, but the British system is _Name, Number & road, Town, County, Postcode_ (or replace the town & county with a city). All that is strictly necessary is the postcode and house number - and this is often all that’s needed when buying stuff buy phone or online. But, as has been pointed out earlier, having the rest of the information allows for errors. (I’ve also seen address labels printed out on inkjets, and smudged in the rain to the point where little of the text is visible. But they still arrived.) ---
**Author:** ![Crandolph](https://avatars.discourse-cdn.com/v4/letter/c/7cd45c/32.png) [@Crandolph](https://boards.straightdope.com/u/Crandolph)\ **Post date:** [April 15, 2005, 5:54pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490/16 "2005-04-15T17:54:49Z")
Credit where credit is due, the USPS is _good_ at getting things where they belong. I once got an envelope that had the wrong zip code, had my street address 10,000 blocks off the correct number :eek: (in theory) & my name misspelled in two places. It wasn’t even much delayed… The more info they have, the more likely the package gets where it’s going. [More info than you ever wanted](http://www.exeter.ac.uk/german/abinitio/chap11-14.html) on German addresses. ---
**Author:** ![elmwood](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/elmwood/32/3060_2.png) [@elmwood](https://boards.straightdope.com/u/elmwood)\ **Post date:** [April 15, 2005, 5:59pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490/17 "2005-04-15T17:59:07Z")
> [@Mehitabel](#): > > Now, if the person is _really_ old-fashioned they’ll use the even older multi-letter abbreviations for the states, like Calif., O., Tex., Ark… You can get even older than that. As late as the 1980s, I was getting holiday cards from elderly relatives, that included the old postal zone in the address (“Buffalo 15, N.Y.”). I also recieved letters with just the word “City” in place of the city, state and Zip; apparently at one time it was acceptable to use “City” or “Town” alone for mail that didn’t cross municipal boundaries. Judging from the alien-looking European addresses I’ve seen, the order of a North American postal address may seem odd; the elements of the address aren’t in the order of smallest to largest geographical area. Take, for instance: Cecil Adams 11 E Illinois Av Chicago IL 60611 A Zip code covers a smaller area than the community, but it comes last in an address. Logically, an address should look like: Cecil Adams 11 E Illinois Av 60611 Chicago IL European-style addresses don’t follow the smallest-to-largest order, either. If the Reader was in Germany, the address would look something like: Cecil Adams Illinoißtraße 11 60611 Chicagoburg British addresses are a mystery to me, because the include several geographic place names; I don’t know if they’re broken down by municipality/council, neighborhood, county or what. Cecil Adams 11 Pillory Close Off Diddling Doperham Swallow-on-Cleese St. Nigel M4K 8SP Dextershiremere If there’s a postal addressing system I’d like explained to me, it’s the one the Brits use. ---
**Author:** ![aerodave](https://avatars.discourse-cdn.com/v4/letter/a/f08c70/32.png) [@aerodave](https://boards.straightdope.com/u/aerodave)\ **Post date:** [April 15, 2005, 6:00pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490/18 "2005-04-15T18:00:04Z")
This jsut got hit on a coupel posts above, but I’ll reiterate: The +4 part of the expanded zip doesn’t narrow it down to a particular house, usually. In my suburban neighborhood, I share my +4 with the rest of my block on the same side of the street, which ends up being about 5 or 6 houses. If I go to the PO, and look at the Big Book O’ ZIP Codes, it shows the address range that my +4 is assigned to. Also, in reply to the OP, it’s not exactly correct to consider the state abbreviation as a “Prefix” for the ZIP. It’s not a part of the ZIP at all, but rather a part of the location. It’s more like (Austin, TX) (78711) than it is (Austin) (TX 78711). Of course, every ZIP is going to be uniquely assigned to a state, allowing you to figure the state out based on the 5 digits. But it’s still included for other important reasons, _addressed_ (no pun intended) above. ---
**Author:** ![sciguy](https://avatars.discourse-cdn.com/v4/letter/s/e68b1a/32.png) [@sciguy](https://boards.straightdope.com/u/sciguy)\ **Post date:** [April 15, 2005, 6:00pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490/19 "2005-04-15T18:00:48Z")
Zip codes are unique, in that every code covers a specific area, and there are no two separate areas with the same code. Using a quick back-of-the-envelope calculation (just dividing the US’s surface area by number of codes), each 5 digit zip code will cover 37 square miles (96 square km), and a 9 digit zip covers .0037 sq miles (.096 sq km). I’m pretty sure the post office actually does it by population density, there’s not much sense using the same coverage for low population areas like Wyoming as for dense areas like Manhattan. But even with the “even coverage” method, a nine digit code covers roughly the area of around 10-25 homes. In theory, the post office can probably deliver a letter with just the street address (especially if it’s an apartment complex) and the 9 digit zip. In practice, having “overlapping” information such as zip + city/state helps in the same way as error correction bits in data files. If part of the address is illegible or incorrect (due to bad handwriting, misspelling, damage to envelope), then the extra information can clear things up. I’m not sure if the post office explicity requires the extra information, but it would certainly speed up the processing. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [April 15, 2005, 6:02pm UTC](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490/20 "2005-04-15T18:02:47Z")
> [@PigBoy](#): > > It’s not strictly necessary to use the official two letter abbreviations, is it? I frequently write out the whole state name if it’s a short one. You’re supposed to stick rigidly to the two-letter abbreviations. Similarly the USPS has a [load of other abbreviations](http://www.usps.com/ncsc/lookups/usps_abbreviations.htm) that it wants people to use, e.g STE for Suite, TRLR for trailer and so on… [Next page](https://boards.straightdope.com/t/why-put-americans-use-state-prefixes-in-front-of-zip-codes/299490.md?page=2)