River Forest, IL has a population of 11,217 and is the 3,605th largest city in the United States. The population density is 4,523 per sq mi which is 1935% higher than the Illinois average and 4893% higher than the national average. The median age in River Forest is 41 which is approximately 9% higher than the Illinois average of 37. In River Forest, 62% of the population over 15 years of age are married, 87% speak English and 5% speak Spanish. 65% of River Forest residents were born in Illinois, 26% were born out of state, 1% were born outside of the United States and 9% were foreign born.