Forsyth, IL has a population of 3,421 and is the 8,160th largest city in the United States. The population density is 1,105 per sq mi which is 397% higher than the Illinois average and 1120% higher than the national average. The median age in Forsyth is 46 which is approximately 23% higher than the Illinois average of 37. In Forsyth, 76% of the population over 15 years of age are married, 92% speak English and 2% speak Spanish. 67% of Forsyth residents were born in Illinois, 25% were born out of state, 1% were born outside of the United States and 8% were foreign born.