API Technical Discussions

COUNTY lookup by valid street address

I am looking for a solid WebService API method that will allow me to submit an http request with a pre-validated US Street/City/State/Zip address and return COUNTY in xml or json about 200 times per work day.It looks like the US Census API may do it? Is the data current enough? What might a request look like? Many thanks in advance.


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  1. Comment

    The Census Geocoder API should meet your needs. The data are updated twice a year and contain the most current address ranges that the Census Bureau has. The address ranges are built from our address list and there are some limitations to the addresses you will find. The documentation for using the Census Geocoder API can be found at http://geocoding.geo.census.gov/geocoder/Geocoding_Services_API.pdf (PDF).

    More information about the Geocoder can be found at: http://www.census.gov/geo/maps-data/data/geocoder.html.

    A valid request format would look like this:


    Here's one example of how to get a JSON return of the county for an address recent snapshot of our data:


    There are other formats explained in the documentation linked above. The documentation also includes the valid values for the benchmark, vintage, and layer id's.

    If you have additional technical questions about the geocoder you can contact the programmers at: geo.geocoding.services@census.gov.

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    1. Comment
      Community Member ( Idea Submitter )

      Jennifer, thank you. It looks like COUNTY is here in the response:"FUNCSTAT":"A","NAME":"Prince George's County", correct? Two more questions: 1) How reliable is this web service; is it up most USA business hours and is it normally responsive (not overloaded). 2) Can you suggest a way to shorten the http request so that the response containing COUNTY is shorter? I have received my API key and am excited to dig in to the docs. Thanks again for the start!

  2. Comment

    Sorry for the delay in responding, I wanted to run this by a few people.

    The "NAME" field is the county name with "county" appended (or other appropriate descriptor such as "parish"). The "FUNCSTAT" code tells you whether the area is an active government, statistical entity (county equivalent such as many areas in Alaska), etc. The "BASENAME" field gives you the county name without the descriptor appended (e.g. Prince George's instead of Prince George's County).

    1. The web service is up generally 24/7 and is responsive. We do generally have to take the servers off-line or rotate them off-line once a month for a few hours where it may be slow or unresponsive, but we attempt to have any planned maintance completed before 6 am Eastern time.

    2. Unfortunately at this time the response cannot be shortened. We are continually working on improvements to the tool (this is our first iteration) and we will add this comment to the list of improvements.

    Please let us know if you have any further questions.


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      Community Member ( Idea Submitter )

      Jennifer, great info once again, thank you. The biggest question I have left is regarding commercial addresses. I want to verify that this database lacks many or most US commercial / business addresses, correct?

  3. Comment

    Sorry, I completely overlooked your message.

    The tool has a much better match rate for residential addresses since that is the primary focus of our address needs. However, we are adding in more commercial addresses and you should see increased match rates in the future.

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