Libertyville, IL has a population of 20,435 and is the 2,123rd largest city in the United States. The population density is 2,319 per sq mi which is 943% higher than the Illinois average and 2460% higher than the national average. The median age in Libertyville is 45 which is approximately 19% higher than the Illinois average of 37. In Libertyville, 67% of the population over 15 years of age are married, 88% speak English and 3% speak Spanish. 60% of Libertyville residents were born in Illinois, 30% were born out of state, 1% were born outside of the United States and 9% were foreign born.