To create the CZMP counties shapefile, we initially used a three-step process: (1) the 2008 TIGER/Line shapefile (U.S. Census Bureau, 2008) provided shapefile information for all counties and equivalent entities in the 50 states, District of Columbia, and U.S. territories; (2) appendix A of the “Coastal Zone Management Act Performance Measurement System: Contextual Indicators Manual” (National Oceanic and Atmospheric Administration, Office of Ocean and Coastal Resource Management, 2009) provided a list of CZMP counties and equivalent entities, organized by state or territory, which was used to create an initial subset of the TIGER/Line shapefile; and (3) this subset was reconciled as necessary with “Substantial Changes to Counties and County Equivalent Entities: 1970–Present” (U.S. Census Bureau, n.d.)—a chronological list of additions, deletions, name changes, and boundary changes—to produce a shapefile of 491 CZMP counties and equivalent entities, represented by 500 polygons (in the U.S. Virgin Islands, American Samoa, and the Northern Mariana Islands, CZMP lumps together islands that have different FIPS codes in the shapefile).

In 2009, selected counties and equivalent entities were redrawn or renamed in preparation for the 2010 census (most notably the boroughs, census areas, and municipalities of southeastern Alaska), necessitating a revision of the recently completed CZMP counties shapefile. The CZMP counties shapefile was updated to conform with the newly released 2009 TIGER/Line shapefile (U.S. Census Bureau, 2009) by using the ArcGIS^® “select by location” command: the 2009 TIGER/Line polygons were selected if their centroids were contained within one of the polygons of the 2008 CZMP counties shapefile; all other polygons within the 2009 TIGER/Line shapefile were eliminated, thus producing an updated CZMP counties shapefile (now with 492 CZMP counties and equivalent entities, represented by 501 polygons). This simple procedure can be repeated by end users of the CZMP counties shapefile whenever additional updates become necessary.

The voluntary withdrawal of Alaska from the CZMP on July 1, 2011 (National Oceanic and Atmospheric Administration, Office of Ocean and Coastal Resource Management, 2012), affected 25 county equivalents in the State—boroughs, census areas, and municipalities—and left us with a difficult choice. Should these Alaskan county equivalents be removed from the shapefile, thus eliminating a useful tool for subdividing the longest coastline in the U.S.? We decided against this course of action and instead present the shapefile with a caveat: current for the ground condition in 2009.