The Bureau of Transportation Statistics (BTS), which is a service of the United States Department of Transportation (US DOT), maintains a list of US state and country codes, named World Area Codes (WAC).
World Area Code (WAC) look-up table
The WAC codes themselves are listed in the so-called WAC look-up table.
World Area Code (WAC) table
The WAC table provides quite a few more details.
On OpenTravelData (OPTD)
From the BTS
- Go to http://www.transtats.bts.gov/DL_SelectFields.asp?Table_ID=315&DB_Short_Name=Aviation%20Support%20Tables
- Select all the fields
- Download the file. The file name should be something like 495998804_T_WAC_COUNTRY_STATE.zip
- Extract the compressed file
Area codes for every airport
The BTS also maintains the mapping between the most important airports and those WAC codes, in a dedicated CSV file