Flagler County was created in 1917. It was named for Henry Morrison Flagler, a famous railroad builder who built the Florida East Coast Railway.
In 1998, when two brush fires threatened to become one huge brush fire in Flagler County, a mandatory evacuation was ordered for the entire county. This was the first and so far the only time a whole county was evacuated in Florida.
Since then, Flagler County was listed as the fasting growing County in the U.S. by percentage of 2000 population.
The county has a total area of 571 square miles (1,478 kmē), of which, 485 square miles (1,256 kmē) of it is land and 86 square miles (222 kmē) of it is water.