At the global view there is not much difference between using ZIP code boundaries and county boundaries to view USA ACBL districts.  Let's take a closer look.  The closer look should not only show more boundary variation between these two schemes, but it will also afford District Directors an opportunity to look at the boundaries more clearly and make corrections.  The maps are pictures of the database.  A correct database (or as correct as possible) is important in streamlining efficiency of information transmission from headquarters to members, and also within headquarters and among members.

[Albers Equal-Area Conic projections (Conterminous USA); Clarke 1866 Spheroid; Central Meridian, -96; Reference Latitude, 37.5; Two Standard Parallels, 29.5 and 45.5.]

Again, the visual differences, between using districts defined by ZIP codes and by counties, are not large from the National viewpoint.  They may, however, be large to the people who live in the zones of no overlap.  The next sections will take a closer look at these differences.  While the maps on this page do reflect one picture of various ACBL databases, they are not the direct picture:  they have been "retouched" so they are easier to read.  To see the raw maps, and to see a technical discussion of how the raw maps were filled in (no doubt introducing some errors), please go to this link.  Constructive response from those who know of boundary alterations that need to be made will be much appreciated.

The next set of two maps shows ZIP Code and County boundaries, respectively, within District boundaries displayed above.  That way, the reader can gain some appreciation of the variation in pattern depending on which small units are chosen as a fundamental unit (each choice has merits).  In the set of two maps below, large differences are evident in pattern within each District.  ZIP code areas provide a much finer partition of space than do counties; indeed, in the map below, the ZIP code boundary lines fill space in many places and render the interior color invisible.  Large city location is more evident with the ZIP code partition than with the county partition.  Although ZIP code areas do not necessarily nest nicely inside county boundaries, many of the edges of the District boundaries did benefit from such nesting.  The maps below show the large differences between data collected by ZIP codes and data collected by county. 
Spatial unit selection is a basic issue.

[Albers Equal-Area Conic projections (Conterminous USA); Clarke 1866 Spheroid; Central Meridian, -96; Reference Latitude, 37.5; Two Standard Parallels, 29.5 and 45.5.]


This Atlas of international, national, and regional bridge maps is designed for visualizing information about the broader bridge-playing population.  Selected problems are considered using the evidence of maps.  These maps are tied in the computer to various ACBL databases and U.S. Census databases.  Thanks to Jay Baum, ACBL CEO, Rick Beye, Carol Robertson, Richard Oshlag, and Ed Evers, ACBL, for providing the materials directly to Sandra Arlinghaus, who then created the map sets using GIS software (ESRI, ArcView 3.2) that forges a dynamic link between underlying database and outline base map.  Graphic adjusments of various kinds were made in Adobe PhotoShop or Adobe Illustrator.

The linked materials display data from the ACBL national data base.  If you are looking for local materials related to finding a bridge club, please go to maps created originally by Jim Lahey, former District 12 Webmaster, and maintained by Alan W. Bau, current District 12 Webmaster (  If instead, you are looking for materials about the broader bridge-playing population, at the regional and national levels, you are in the right place!

Click here to send an email to Bill Arlinghaus
Click here to send an email to webmaster of this page