Key Largo, FL has a population of 10,024 and is the 3,936th largest city in the United States. The population density is 831 per sq mi which is 183% higher than the Florida average and 818% higher than the national average. The median age in Key Largo is 53 which is approximately 27% higher than the Florida average of 42. In Key Largo, 58% of the population over 15 years of age are married, 78% speak English and 20% speak Spanish. 31% of Key Largo residents were born in Florida, 52% were born out of state, 2% were born outside of the United States and 15% were foreign born.