County Definitions

Data from several different sources were used in this publication, and one of our chief methodological concerns was ensuring comparability of county definitions across datasets. We used the Federal Information Processing Standard (FIPS) codes to link county definitions across datasets, and to reconcile differences. For the majority of states, there was 100 percent comparability in county definitions among all the datasets used. Details about modifications to county definitions for specific states appear below.

The following cities were retained as independent cities and the FIPS codes were modified to conform to the geographic database.

2. Alaska
Due to differences in county coding over time, and differential coding among the various data sources, several other changes were also made to county FIPS codes. The coding changes are indicated in the following tables. In 1994 the original Aleutian Islands (county code 2010) was subdivided into Aleutian Islands East (county code 2013) and Aleutian Islands West (county code 2016).

3. Arizona

4. Hawaii

5. Virginia 
Virginia is comprised of counties and independent cities that are treated as county–equivalents in many datasets. Many of these cities are difficult to represent on a map because of their small land area. Therefore, the spatial geometry for most of Virginia independent cities was removed from the geographic database and data for those cities was collapsed into those counties with which they are most geographically associated. We followed the conventions of the 1996 Area Resource File. The changes made to FIPS codes to combine Virginia independent cities with their surrounding or adjacent counties are shown in the table below.

5. Yellowstone National Park

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Date last reviewed: 05/12/2006
Content source: Division for Heart Disease and Stroke Prevention, National Center for Chronic Disease Prevention and Health Promotion