Riverside, IL has a population of 8,779 and is the 4,346th largest city in the United States. The population density is 4,437 per sq mi which is 1896% higher than the Illinois average and 4798% higher than the national average. The median age in Riverside is 42 which is approximately 12% higher than the Illinois average of 37. In Riverside, 64% of the population over 15 years of age are married, 81% speak English and 10% speak Spanish. 70% of Riverside residents were born in Illinois, 16% were born out of state, 3% were born outside of the United States and 11% were foreign born.