Flagler county was ranked the fastest-growing county in the nation by the US Census Bureau from 2000 to 2005 , with a 53.3 % change , with a July 1 , 2005 population estimate at 76,410 . Flagler county was ranked the fastest-growing county in the nation by the US Census Bureau from 2000 to 2005 , boasting a 53.3 % change , with a July 1 , 2005 population estimate at 76,410 .