Carthage, IL has a population of 2,513 and is the 9,817th largest city in the United States. The population density is 1,035 per sq mi which is 354% higher than the Illinois average and 1043% higher than the national average. The median age in Carthage is 47 which is approximately 26% higher than the Illinois average of 37. In Carthage, 66% of the population over 15 years of age are married, 96% speak English and 2% speak Spanish. 65% of Carthage residents were born in Illinois, 33% were born out of state, 0% were born outside of the United States and 2% were foreign born.