A National ANSI File is available for download.
This file contains comma-delimited records for each state and county. The records are of the format:
State Abbreviation, State ANSI, County ANSI, County Name and Legal Statistical Area Description, ANSI Class Code
The inventory, names, and codes for counties and equivalent areas change periodically. Please review Substantial Changes to Counties and County Equivalent Entities: 1970-Present.