043 - Geographic Area Code

When cataloging materials that are about (or partially about) a place, subject headings are assigned (in 6XX tags) to represent those geographic qualities. For example (these are Library of Congress authorized headings, by the way):

• Great Lakes Region (North America)
• Geology ǂz Nunavut ǂz Baffin Island
• Lunar petrology
• Oaxaca (Mexico) ǂx Antiquities
  

In addition to the 6XX tags (which are a huge topic that I am not dealing with at this point), a cataloger may want to code the geographical qualities of an item's subject and to do that a Geographic Area Code (GAC) is used and is found in the 043 tag. You can interpret the codes found in subfield a of the 043 tag by consulting the MARC Code List for Geographic Areas.  

 

GACs are seven-character strings, consisting of lowercase alphabetic characters and hyphens. In a MARC record all 7 characters must be present so if a GAC is shorter than 7 characters it will have hyphens added to the end to fill out the required characters. These are hierarchical designations, so the longer the GAC the more specific the place. There are 19 places designated by single-character codes.

"The codes are constructed to provide a hierarchical arrangement of geographic and political entities. There are three levels possible in the codes. Most codes are at the first level and represent continents, regions, geographic features, and some national level political jurisdictions. A first level code consists of one or more lowercase alphabetic characters. 

Second level codes represent regions and national level political entities located within the
entity represented by the first level code. A second level code consists of a first level code,
followed by one hyphen, followed by the code for the second level entity. At the second level, a two letter code generally represents a country, and a three letter code represents a region within a country.  

Third level codes represent first order political divisions of countries represented by a second level code. A third level code consists of a first level code, one hyphen, a second level code, one hyphen, and a third level code. Third level codes always consist of two lowercase alphabetic characters."
                             -- excerpted from the Library of Congress' Introduction to GACs

 As an example, let's break down the GAC that would be used in conjunction with the LC subject heading Geology --Nunavut --Baffin Island.

• n is a first level code indicating a place in North America
• n-cn is a second level code indicating a place in Canada
• n-cn-nu is a third level code specifically indicating the territory of Nunavut 
• "first order political divisions" is as specific as GACs get, so Baffin Island (the 5th largest island in the world which is part of Nunavut) doesn't have a code and the one that includes it (n-cn-nu) would be used
  

 Here are the GACs for our other geographic subject examples:

• nl-----   (Great Lakes Region (North America))
• zmo----  (Lunar petrology) -- the moon has a GAC
• n-mx---   (Oaxaca (Mexico) -- Antiquities) 

Why, you may wonder, doesn't Oaxaca have a level 3 code? Because only a handful of 2nd level codes have been further subdivided. Those are China (a-cc), United States (n-us), Great Britain (e-uk), Australia (u-at), and Canada (n-cn).