St. Augustine, FL has a population of 13,440 and is the 3,081st largest city in the United States. The population density is 1,425 per sq mi which is 307% higher than the Florida average and 1473% higher than the national average. The median age in St. Augustine is 42 which is approximately 2% higher than the Florida average of 41. In St. Augustine, 45% of the population over 15 years of age are married, 93% speak English and 4% speak Spanish. 38% of St. Augustine residents were born in Florida, 53% were born out of state, 2% were born outside of the United States and 7% were foreign born.