St. Augustine, FL has a population of 13,867 and is the 3,017th largest city in the United States. The population density is 1,470 per sq mi which is 401% higher than the Florida average and 1523% higher than the national average. The median age in St. Augustine is 43 which is approximately 3% higher than the Florida average of 42. In St. Augustine, 43% of the population over 15 years of age are married, 91% speak English and 6% speak Spanish. 37% of St. Augustine residents were born in Florida, 54% were born out of state, 1% were born outside of the United States and 8% were foreign born.