County and State FIPS codes

Kieran Healy (@kjhealy)

Summary

• Three CSV files with some basic FIPS identifying information for US States (state_fips_master.csv), Counties (county_fips_master.csv), and both together (state_and_county_fips_master.csv). I got sick of constantly having to write code to match on one or other of these identifiers in order to merge data files (e.g. for maps). So this can serve as a basis for harmonizing files that use one, some, or some variant of these identifiers. For example, sometimes leading zeros are omitted in the FIPS, sometimes not; sometimes the FIPS is coded in data as one number, sometimes as a character-vector of digits, sometimes as two separate state and county numbers, and so on. The Census also has its own supra-state units (regions and divisions). These files make it easier to merge and match to data indexed in one or other of these ways.

Files

The county_fips_master.csv file looks like this:

fips	county_name	state_abbr	state_name	long_name	sumlev	region	division	state	county	crosswalk	region_name	division_name
1001	Autauga County	AL	Alabama	Autauga County AL	50	3	6	1	1	3-6-1-1	South	East South Central
1003	Baldwin County	AL	Alabama	Baldwin County AL	50	3	6	1	3	3-6-1-3	South	East South Central
1005	Barbour County	AL	Alabama	Barbour County AL	50	3	6	1	5	3-6-1-5	South	East South Central
1007	Bibb County	AL	Alabama	Bibb County AL	50	3	6	1	7	3-6-1-7	South	East South Central
1009	Blount County	AL	Alabama	Blount County AL	50	3	6	1	9	3-6-1-9	South	East South Central
1011	Bullock County	AL	Alabama	Bullock County AL	50	3	6	1	11	3-6-1-11	South	East South Central

• crosswalk is just a concatenation of region, division, state, and county identifiers, sometimes useful for merging with files that do not include a full numeric FIPS code, but instead split it up by state and county.

The state_fips_master.csv file looks like this:

state_name	state_abbr	long_name	fips	sumlev	region	division	state	region_name	division_name
Alabama	AL	Alabama AL	1	40	3	6	1	South	East South Central
Alaska	AK	Alaska AK	2	40	4	9	2	West	Pacific
Arizona	AZ	Arizona AZ	4	40	4	8	4	West	Mountain
Arkansas	AR	Arkansas AR	5	40	3	7	5	South	West South Central
California	CA	California CA	6	40	4	9	6	West	Pacific
Colorado	CO	Colorado CO	8	40	4	8	8	West	Mountain

And the state_and_county_fips_master.csv file looks like this:

fips	name	state
0	UNITED STATES	NA
1000	ALABAMA	NA
1001	Autauga County	AL
1003	Baldwin County	AL
1005	Barbour County	AL
1007	Bibb County	AL

• This file includes the US overall FIPS code (00000) and each of the state codes as five digit numbers, in order. The country's name and the names of the states are in all-caps.

Some Gotchas

When merging and filtering county-level data, there are a few things that might bite you, as they have bitten me.

• Beware of confusion that may arise when trying to merge FIPS encoded as a character (e.g. State code "04") and FIPS encoded as an integer (4).
• Counties or Parishes with "Saint" or "St" in their names are sometimes inconsistently spelled or abbreviated.
• Some places have "La" in their name. It's LaSalle Parish (LA), but La Salle County (TX), but LaSalle County (IL). These are sometimes written incorrectly.
• Doña Ana County, NM, has the only "ñ" in America's county names. It can get mangled in the character encoding of text files (especially old ones), or converted to a mere "n".
• It's "District of Columbia", not "Washington DC".
• The District of Columbia has a State-like FIPS code (11) and a County-like one (11001).

In any case, you are never trying to match on character strings when merging data that should have unique numerical identifiers. Right?