ZIP codes and post offices

Factual Questions
1

I hope I can word this clearly enough. Basically I’d like to know about the organization of ZIP codes.

I’ll use the example of my home to ask my questions. I live in a ZIP code beginning with 454. All the 454 ZIP codes are in an area including and surrounding Dayton, Ohio. All these mailing addresses as far as I know can say “Dayton, Ohio” regardless of whether the address is actually in Dayton. (I think Cincinnati is the same way with 452 ZIP codes.) There is a large post office downtown as well as various smaller post offices here and there. Surrounding the 454’s are mainly 453’s. Each of these seems to have its own post office name. I am in a suburb with a 454 ZIP code, so my address is likely to be given as “Dayton,” while several different suburbs are in 453 ZIP codes and their addresses will say Miamisburg, Fairborn, etc., i.e., not “Dayton.”

So, my questions:

  1. Am I correct in assuming that there are places in which all ZIP codes beginning with the same 3 digits will have address place names of the central city/post office? If so, what determines when this is the case and when it is not?
  2. Since all the 454’s are “Dayton,” does all mail to and from 454 ZIP codes go through the main Dayton post office?
  3. In cases where each individual ZIP code is associated with a different post office, does mail go to any similar central place?
  4. Or, if some of my assumptions are incorrect, does the ZIP code not really matter? For example, will mail from some of the 453’s near Dayton end up going through Dayton anyway?
2

If you go to your local post office, they should have a nationwide ZIP code book published by USPS. Before each state’s listing there will be a map with the rough boundaries of each three digit prefix.

So in Ohio, Dayton is a regional processing center and handles 454. But 453 and 455 are processed in Dayton also.

But a quick check of a list of Ohio cities, I can see that Alpha is 45301, so you can write the name of the actual city instead of Dayton.

From the map, it looks like Cincinnati handles 450, 451, 452, and 470. Chillicothe handles 456. Athens handles 457. Columbus gets 430, 431, 432, and 433. Zanesville is 437-438. Steubenville is 439. Canton is 446-447. Youngstown is 444-445. Cleveland is 440-441. Akron is 442-443. Mansfield is 448-449. Toledo is 434-435-436 and Lima is 458.

3

Check this out.

http://acg.media.mit.edu/people/fry/zipdecode/

Hard to work but pretty neat.

4

Generally, the country is divided into ten major zones for Zip Code. “0” is New England and New Jersey, “1” is New York and Pensylvania, etc.

The second two digits are major cities (and mail centers within that zone). Thus, in NY, “122” is Albany, “123” is Schenectady. “120” and “121” are for the general post office within that area.

The next two digits depend. In a general post office, they often are smaller PO in roughly alphabetical order. IIRC, there are gaps in case a new community is founded.

Within a city PO, it’s determined by substation.

5

Without going into the Post Office’s specialized vocabulary, every major population center and a wide selection of smaller population centers constitutes a regional center, where mail is processed for the suburbs, small towns, and rural areas around it. It is assigned from one to quite a few three-digit codes.

If the community is itself relatively small, having only one or two five-digit Zip codes, then the surrounding area will share the same three-digit code as the city. For example, Watertown NY is 13601, with Fort Drum, the nearby Army base, having 13602 and 13603 codes. The surrounding towns and villages in Jefferson and St. Lawrence Counties (and northern Lewis County) also have 136xx codes assigned in alphabetical order, Adams being 13605 and Woodville 13698.

Larger cities get two or three adjacent three-digit combinations assigned to their region. In general, there are three, the first two being the sets assigned to the small towns and rural areas surrounding and the third to the city proper. Syracuse, NY, for example, services a multi-county area with codes beginning 130xx and 131xx, the city itself and a few suburbs getting 132xx codes. Each neighborhood post office in Syracuse gets a code of 13203, 13404, etc.

Albany, NY, with the same pattern, services a small town/rural area with 120xx and 121xx codes, Albany city and a few suburbs being 122xx codes, and the nearby city of Schenectady getting the 123xx codes. (General Electric’s HQ and plants in Schenectady have 12345 zip code assigned to them, by the way, for those who collect that sort of trivia.)

New York City and a few other major cities may have a large group of adjacent 3-digit codes assigned. All the 10xxx and some 11xxx codes are assigned to parts of NYC.

Most Post Offices have a single Zip code assigned to them, servicing the PO boxes in their lobby, the home deliveries that they are responsible for, and the rural deliveries that may operate out of that PO. Some of the larger ones have two or more Zip codes. The Crabtree Valley PO in Raleigh NC, for example, has 27612 as its main number, and 27622 covering its PO boxes.

Many Post Offices use a standard pattern of assigning Zip+4 coding: [ul][li]The PO boxes located at that PO use the lowest numbers, assigned according to the box number with leading zeroes to constitute a four-digit number. PO Box 3 takes a +4 code of -0003, PO Box 750, -0750. [/li][li]The range from 1000 up is assigned to city delivery, with the lowest numbers being downtown and the 2000 and higher ranges to outlying residential neighborhoods. []Numbers up in the 5000-7000 ranges are exurban. [/li][li]Rural delivery routes are in the uppermost range, with the -9700 series for RR 1, the -9600 for RR 2, and so on. -98xx numbers are used for rural routes where the box number is not known, -9801 being RR 1, 9802 RR 2, and so on. [/li][]-9998 is the invariable address of the Postmaster’s office for that PO, and -9999 is General Delivery at that PO.[/ul]

6

Thanks, I think I understand now. Is there any official list of which numbers are assigned to each regional center? I have a GIS map of zip codes, so I’ve been looking at that to see where everything is.

I don’t think it’s actually necessary for me to write “Dayton” for my address (I usually don’t); it’s just that when a computer or something spits out the address, it will say Dayton. But with a 453 like Alpha I think it would always say Alpha and never Dayton.

It’s interesting that you mentioned Alpha. Alpha’s is a tiny zip code covering no more than a couple hundred residents in what was a very small village from the 19th century. Today Alpha is not its own “place,” but rather is part of the city of Beavercreek (where I live), which is a big fat suburb. However, it still has a post office in what is essentially a small house. The smart people around here will go there to avoid the lines at the bigger post offices. I think there are enough such people to drive the woman running the place crazy from too much work, at least at this time of year. Alpha also confuses things for me further because often mail going from there will be postmarked “Cincinnati.”

7

While not “official”, you should be able to see which regional centers service which zip codes here.

8

I just mentioned Alpha, because it was the first one on the list that was a 453.

9

Check this out.

10

That’s strange - the “Alpha mail” should be the dominant post office …

11

ZipperJJ, that link is friggin’ neat.

Whoa, deja vu! :wink:

12

Postal worker checking in.

Bear in mind that zip/postal codes are becoming obsolete anyway. They’ll be around for a while, but not forever. If you look at the average letter you receive these days, it is covered in bar codes of various types. Each delivery point (individual address) here in Australia has its own unique code. I am sure the situation in the United States is identical. Zip codes are really only useful for certain hand-addressed letters. Or should I say, numeric zip codes in human readable form are only useful for that. They fulfil their main function these days in forming a part of a bar code.

An interesting manifestation of this is that Australia (and other places like South Africa) have been able to cling to a mere four digit post code. Admittedly we are smaller countried than the US, but not so small that we weren’t starting to run out of available codes. We were right at the point of biting the bullet and going for a US-style nine digit code system when technology caught up and saved us. Now the bar codes do the same work that the extra digits on US zip codes do. As the US uses barcoding too, then zip’s days are numbered (well, actually not numbered ironically).

13

Yeah, I figured that… but it’s still interesting! It also finally led me to connect the dots as to just why the hell Alpha is 45301 when adjacent zip codes are 45434 and 45385. I don’t know why I never thought alphabetically. :smack:

14

Pigboy,

This official link http://zip4.usps.com/zip4/welcome.jsp is handy for more specific information. it’ll tell you things like whther “Dayton” is a proper name for your suburb or whether you’re supposed to use “Happy meadows” or whaever the town name is.

The cool thing about the PO is tthat although they have rules & procedures for how we’re all supposed to address stuff, most people can flaut most of the rules most of the time and the mail still gets there anyhow. It’s a very fault-tolerant system.

As en example, my Mom resides in one city and her servicing PO is in the adjacent city. I can put either city’s name and/or zip code in any combination and she still gets the mail with 100% reliability. Try that with TCP/IP!