Midlothian, IL has a population of 14,830 and is the 2,866th largest city in the United States. The population density is 5,260 per sq mi which is 2266% higher than the Illinois average and 5706% higher than the national average. The median age in Midlothian is 37 which is approximately 1% lower than the Illinois average of 37. In Midlothian, 51% of the population over 15 years of age are married, 81% speak English and 16% speak Spanish. 82% of Midlothian residents were born in Illinois, 9% were born out of state, 0% were born outside of the United States and 9% were foreign born.