Port St. John, FL has a population of 11,223 and is the 3,602nd largest city in the United States. The population density is 2,896 per sq mi which is 886% higher than the Florida average and 3097% higher than the national average. The median age in Port St. John is 42 which is approximately 2% higher than the Florida average of 42. In Port St. John, 54% of the population over 15 years of age are married, 91% speak English and 6% speak Spanish. 38% of Port St. John residents were born in Florida, 54% were born out of state, 3% were born outside of the United States and 5% were foreign born.