Hi everyone,

we’re big fans of Twitter (where you can find us as @OpenCage), and for for the last few months every week or so we’ve been doing educational threads about our service or common questions we get.

Here are a few examples. Threads about

those are all great, and many people gave us feedback that they find threads like that very informative (thx!), but yesterday, the final Friday of the month, we decided to lighten things up with some geotrivia.

We posted a question that had come up this week while debugging a user’s geocoding issue:

The geotrivia question:

How many two letter US postal state abbreviations are also ISO country codes?

We started things off with the example of CA which is the code for the state of California and the ISO code for Canada.

I should note that we didn’t count things like PR which is of course the postal state code of Puerto Rico and the ISO code of Puerto Rico. We’re looking for postal state codes that correspond with different countries.

Of course this question can easily be answered by a bit of searching or simply comparing the lists on a source like Wikipedia, but the whole point of the twitter thread is people are supposed to try to do it just from knowledge. Lots of people played along, and it was some light-hearted fun to close the week out. The answer has a few surprising twists (spoiler, the full list is below).

But it hopefully also served to make two points that are relevant in the context of geocoding.

  • Due to historic anomalies ISO 3116-1 alpha-2 codes (to use the full and correct name) don’t always map to countries. A good example is NC the state code for North Carolina which is the ISO code for New Caledonia, a “special collectivity” of France (background on Wikipedia). We explain the relation ship between ISO codes and our countrycode value in our guide to determining which country GPS coordinates are in.

  • Postal codes and abbreviations don’t always correspond to geographies, though many people use them that way. We cover this a bit in our guide to common misunderstandings about geography and postal codes. In this a case the key example is the “state” code AE which is used by the US postal system for deliveries to American military forces in Europe. It’s of course also the ISO code for the United Arab Emirates.

The whole thing was a lot of fun, and we think we’ll make is a regular event for the final Friday of every month. We will use the hashtag #fridaygeotrivia All suggestions for good trivia questions gladly received!

The geotrivia answer:

  • AE - United Arab Emirates and American Forces Europe
  • AL - Albania and Alabama
  • AR - Argentina and Arkansas
  • AZ - Azerbaijan and Arizona
  • CA - Canada and California
  • CO - Colombia and Colorado
  • DE - Germany and Delaware
  • GA - Gabon and Georgia
  • ID - Indonesia and Idaho
  • IL - Israel and Illinois
  • IN - India and Indiana
  • KY - Cayman Islands and Kentucky
  • MA - Morocco and Massachusetts
  • MD - Moldova and Maryland
  • ME - Montenegro and Maine
  • MN - Mongolia and Minnesota
  • MO - Macau and Missouri
  • MS - Montserrat and Mississippi
  • MT - Malta and Montana
  • NC - New Caledonia and North Carolina
  • NE - Niger and Nebraska
  • PA - Panama and Pennsylvania
  • SC - The Seychelles and South Carolina
  • SD - Sudan and South Dakota
  • TN - Tunesia and Tennessee
  • VA - The Vatican and Virginia

Happy geocoding,