County Adjacency File

Overview:

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).

Download:

Download the County Adjacency File [txt]

File Layout:

The county adjacency file is a national, tab delimited text file.  The list is sorted by County GEOID and then 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:

Notes:

• 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.