High Quality Content by WIKIPEDIA articles! The FIPS county code is the five-digit Federal Information Processing Standard 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, while Ada County, Idaho is number 001, Churchill County, Nevada and Albany County, Wyoming also have the number 001. While there is a Clark County, Idaho with the number 033, there also is a Clark County, Nevada with the number 003 and a Clark County, South Dakota with the number 025. To uniquely identify Clark County, Idaho, you would need to use the state code of 16 plus the county code of 033. Thus the unique identifier for the entire United States for Clark County, Idaho would be 16033.