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County Adjacency File
County Adjacency File
The county adjacency file lists each county, or county equivalent, and which county, or counties, are neighboring. The file includes all 50 states, the District of Columbia, Puerto Rico, and the Island Areas (American Samoa, the Commonwealth of the Northern Mariana Islands, Guam, and the U.S. Virgin Islands).
The Census Bureau resumed production and release of the County Adjacency File product in 2023 in response to multiple requests for this product. There was no release of this product between 2010 and 2023.
File Layout
The 2023 County Adjacency File is a national, pipe delimited text file. The list is sorted by County GEOID, and the neighboring counties are sorted by Neighbor GEOID within each county. The Island Areas appear at the end of the list.
The table below provides the layout of the county adjacency file:
| Column | Column Name | Column Description |
|---|---|---|
| 1 | County Name | 2023 state and county name |
| 2 | County GEOID | 2023 state and county FIPS codes |
| 3 | Neighbor Name | 2023 state and county name of each neighboring county or county equivalent |
| 4 | Neighbor GEOID | 2023 state and county FIPS codes of each neighboring county or county equivalent |
Notes
- Each relationship with a neighboring county is represented as a new data row. A county that is adjacent to two other counties will be listed twice.
- Relationships are listed in both directions. If county ‘12345’ is adjacent to county ‘67890’, then this will appear twice in the file, once with ‘12345’ listed first as the primary GEOID, and then again with ‘67890’ listed first as the primary GEOID.
- In some instances, the boundary between two counties may fall within a body of water, so it seems as if the two counties do not physically touch. These counties are included on the list as neighbors.
- Every county has itself listed as a neighboring county.
Page Last Revised - September 28, 2023
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