county_1990.dta is a crosswalk from 1990 counties to 1990 CZs - it is based off download E6 at http://www.cemfi.es/~dorn/data.htm.

county_2000.dta and county_2010.dta are crosswalks between 1990 CZs and 2000 and 2010 counties - we use the information at https://www.census.gov/geo/reference/county-changes.html

cw_zcta00_cz.dta is a crosswalk between 2000 ZCTAs and 1990 CZs - it uses a crosswalk between ZCTAs and counties from http://mcdc2.missouri.edu/webrepts/geography/ZIP.resources.html

cw_zip99_cz.dta is a crosswalk between ZIP codes in November 1999 and 1990 CZs - it is based on the crosswalk at http://web.archive.org/web/20120914150518/http:/www.census.gov/geo/www/tiger/zip1999.html

List1.xls is a crosswalk between CBSAs and counties in February 2013 - it is available at http://www.census.gov/population/metro/data/def.html

US_FIPS_Codes.csv provides names for counties