Island Lake, IL has a population of 8,025 and is the 4,669th largest city in the United States. The population density is 2,399 per sq mi which is 979% higher than the Illinois average and 2548% higher than the national average. The median age in Island Lake is 39 which is approximately 4% higher than the Illinois average of 37. In Island Lake, 57% of the population over 15 years of age are married, 85% speak English and 10% speak Spanish. 76% of Island Lake residents were born in Illinois, 14% were born out of state, 0% were born outside of the United States and 9% were foreign born.