Districts and Units:  48 States, USA
The first map below shows all units within districts; only the districts are labelled.  In the table below that, maps for a given district fill a single row.  There are 25 rows, one for each district. The first maps in the sequence show labelled units within district boundaries, based on ACBL ZIP code files.  The last map in the sequence, at the end of each column, shows the lack of fit between ZIP Code (yellow stripes) and County (red stripes) district boundaries for each district. 

District 1:  Eastern Canada

District 2:  Ontario, Manitoba, and Bermuda

District 3:  Eastern New York (not New York City), Northern New Jersey.
District 4:  Central New York, Eastern Pennsylvania, Delaware, Southern New Jersey.
District 5:  Western Pennsylvania, Eastern Ohio, Western New York, Western Maryland, and Northern West  Virginia.

District 6:  Washington D.C., Virginia, and Maryland.

District 7:  North Carolina, South Carolina, Georgia, and Eastern Tennessee.

District 8:  St. Louis, Northern Indiana, Central and Southern Illinois, and Paducah KY

District 9:  Florida

District 10:  Mid-south bridge conference.

District 11:  Kentucky, Western Ohio, Central Indiana, and West Virginia

District 12: 
Most of Michigan, Northwestern Ohio

District 13:  Chicago, Wisconsin, and Upper Michigan.

District 14: 
Iowa, Minnesota, North and South Dakota, and Nebraska

District 15:  Southwest Missouri, Kansas, Oklahoma, Western Arkansas, and Northern Texas

District 16: 
Most of Texas, all of Mexico

District 17:  Colorado, New Mexico, Arizona, Southern Nevada, Eastern Utah, West Texas, and Wyoming

District 18: 
Western Canada, Idaho, Montana, and Wyoming

District 19: 
Alaska, Washington State, and British Columbia

District 20:  Washington, Oregon, Nevada, and Hawaii

District 21: 
Northern California

District 22:  Southern California

District 23:  California:  Los Angeles County

District 24: 
New York City and Long Island.

District 25: 
New England

Assignment of district fragments, external to the body of the district, were made to any district which totally contained that fragment.  Similarly, unassigned territories were assigned to the district containing them and were given a "logical" unit number (with that logic based on adjacency patterns).  Such grouping was done merely for visual convenience in looking at district patterns. 
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.

Reprinted from the web page of District 12 Director, Bill Arlinghaus, with permission.
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