Forest Lake, IL has a population of 1,743 and is the 11,837th largest city in the United States. The population density is 4,967 per sq mi which is 2134% higher than the Illinois average and 5382% higher than the national average. The median age in Forest Lake is 41 which is approximately 9% higher than the Illinois average of 37. In Forest Lake, 62% of the population over 15 years of age are married, 83% speak English and 0% speak Spanish. 63% of Forest Lake residents were born in Illinois, 19% were born out of state, 0% were born outside of the United States and 17% were foreign born.