Countryside, IL has a population of 5,965 and is the 5,777th largest city in the United States. The population density is 2,072 per sq mi which is 832% higher than the Illinois average and 2187% higher than the national average. The median age in Countryside is 42 which is approximately 11% higher than the Illinois average of 37. In Countryside, 52% of the population over 15 years of age are married, 70% speak English and 14% speak Spanish. 71% of Countryside residents were born in Illinois, 13% were born out of state, 2% were born outside of the United States and 14% were foreign born.