Source Text File: http://www2.census.gov/geo/docs/reference/county_adjacency.txt
Source File URL: http://www2.census.gov/geo/docs/reference/county_adjacency.txt
Source Page: https://www.census.gov/geo/reference/county-adjacency.html
NBER URL: http://www.nber.org/data/county_adjacency.html
county_adjacency2010 set up by Jean Roth , jroth@nber.org ,  8 May 2017