Zip Codes and FIPS
April 29, 2009 10:33 AM   Subscribe

Where can I get a free dataset of ZIP codes and their corresponding county FIPS codes?
posted by chrisalbon to Work & Money (6 answers total) 5 users marked this as a favorite
If I remember correctly, the Census has this. Try here, there seems to be a lot of info about FIPS in general.
posted by schyler523 at 10:43 AM on April 29, 2009

I haven't been able to find a recent enough free version to be useful in my work, but zipcodeworld has this for a very nominal $60 - more if you need to get monthly updates.
posted by jenkinsEar at 11:03 AM on April 29, 2009

specifically these files.
posted by fozzie33 at 11:04 AM on April 29, 2009

Just one note about the Census resources that people might be recommending: ZIP Code Tabulation Areas (ZCTAs) are not the same thing as ZIP Codes. They are geographically rectified tabulation areas based on ZIP Codes in 2000. Whenever the addresses within a census block had a mixed group of ZIP codes, Census Bureau took the odd ones out and simply reassigned their ZIP code to that of the majority of the other addresses in that block.

Also, ZCTAs were last created in 2000, and have not been updated since. That means all of the ZIPs that have been created, split, subdivided or changed since 2000 are not represented in lists or databases using ZCTAs.

If you need ZIP codes, not ZCTAs, you're not going to get anything from the Census Bureau. The Census Bureau ceased creating ZIP code geographic products after the 1990 Census.
posted by Eldritch at 11:30 AM on April 29, 2009

Oh, and ZCTAs don't include any of the unique ZIP Codes: PO Boxes, mailing facilities, office buildings, etc.
posted by Eldritch at 11:37 AM on April 29, 2009

I've been working on understanding the zip code data for a long time. Eldritch is right - ZCTAs are not going to get you there. To get accurate Zip to FIP data, you really have to buy it because it changes so frequently.

Here's the story why.

Zip codes are controlled by the USPS. They are fundamentally a tool for them to sort mail and get it delivered to the address in the most efficient way possible. The USPS builds zip codes from the bottom up. Almost each building or set of buildings has a specific 9 digit zip code (aka Zip+4) that identifies it specifically. Then the USPS constructs what are called "Carrier Routes," which are litterally the path that the mailman will follow on his delivery schedule that link a set of Zip+4 addresses. A set of carrier routes forms what we know as a 5 digit zip code.

Given new construction, the changing postal patterns, and population trends, the postal service often needs to change the carrier routes; and therefore the boundaries of the zip code will also change. There are thousands of changes each month to the dataset.

County (and state and city and census) are totally different legislative boundaries, and are not coordinated. Not easy to figure out what goes where.

Shameless plug here but I think it adds to the understanding -- I am building a small site that delivers zip code data. We receive our data under license from the United States Postal Service. Each dataset contains over 80 million rows of data! To paraphrase the immortal words of Brody in Jaws, "I think you'll need a bigger computer!"

So what you typically buy from services like zipcodeworld, (and eventually my site) is a crunched database that takes every change at a zip+4 address and correlates it to the zip code and the corresponding county codes. This is usually updated monthly. It's worth the money - but if you want something cheap there are several sites which may sell old zip code data available from an old census database (tiger) which is "close enough for government work!"
posted by mtstover at 7:48 AM on February 16, 2010

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