 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 Albany County is 001, Addison County, Vermont, and Alachua County, Florida, are also 001.To uniquely identify Albany County, New York, one must use the state code of 36 plus the county code of 001; therefore, the unique nationwide identifier for Albany County, New York, is 36001.