The county with the lowest FIPS code in Florida is Alachua County, with 12001. Other counties with low FIPS codes are Baker and Bay, with 12003 and 12005 respectively.
Each US county and county equivalent has a Federal Information Processing Standard, or FIPS, code that identifies it uniquely. The first two digits of the code depend on the State the county belongs to, which is 12 for Florida, while the last three digits are county code within the State. County FIPS codes usually match the alphabetical sequence of the counties within each state, and they are usually odd numbers to allow for new counties.