Park Forest, IL has a population of 21,831 and is the 1,993rd largest city in the United States. The population density is 4,400 per sq mi which is 1830% higher than the Illinois average and 4757% higher than the national average. The median age in Park Forest is 38 which is approximately 2% higher than the Illinois average of 37. In Park Forest, 45% of the population over 15 years of age are married, 92% speak English and 5% speak Spanish. 78% of Park Forest residents were born in Illinois, 17% were born out of state, 1% were born outside of the United States and 4% were foreign born.