Riverdale, IL has a population of 13,047 and is the 3,195th largest city in the United States. The population density is 3,649 per sq mi which is 1542% higher than the Illinois average and 3928% higher than the national average. The median age in Riverdale is 35 which is approximately 6% lower than the Illinois average of 37. In Riverdale, 33% of the population over 15 years of age are married, 97% speak English and 2% speak Spanish. 84% of Riverdale residents were born in Illinois, 15% were born out of state, 1% were born outside of the United States and 1% were foreign born.