As of the 2000 census the population was 79,535 , with an average density of 223.66 \/ kmÂ ( 579.27 \/ sq mi ) , although much of the population is concentrated in a few areas of much higher density , such as the city of Key West , which has 32 % of the entire population of the Keys . The total land area is 137.3 s. As of the 2000 census the population was 79,535 , with an average density of 579.27 \/ , although much of the population is concentrated in a few areas of much higher density , such as the city of Key West , which has 32 % of the entire population of the Keys .