 The FIPS county code is the five-digit Federal Information Processing Standard (FIPS) code which uniquely identifies counties and county equivalents in the United States.The three-digit number is unique to each individual county within a state, but to be unique within the entire United States, it must be prefixed by the state code.This means that, for example, the number 001 is shared by Aitkin County, Minnesota, Adams County, Wisconsin, and Adair County, Iowa.