Middleburg, FL has a population of 13,511 and is the 3,095th largest city in the United States. The population density is 688 per sq mi which is 134% higher than the Florida average and 660% higher than the national average. The median age in Middleburg is 40 which is approximately 3% lower than the Florida average of 42. In Middleburg, 57% of the population over 15 years of age are married, 95% speak English and 3% speak Spanish. 50% of Middleburg residents were born in Florida, 44% were born out of state, 2% were born outside of the United States and 4% were foreign born.