Cary, IL has a population of 17,946 and is the 2,412th largest city in the United States. The population density is 2,885 per sq mi which is 1198% higher than the Illinois average and 3085% higher than the national average. The median age in Cary is 39 which is approximately 5% higher than the Illinois average of 37. In Cary, 64% of the population over 15 years of age are married, 86% speak English and 7% speak Spanish. 74% of Cary residents were born in Illinois, 17% were born out of state, 1% were born outside of the United States and 8% were foreign born.