Third Lake, IL has a population of 1,266 and is the 13,703rd largest city in the United States. The population density is 2,159 per sq mi which is 871% higher than the Illinois average and 2283% higher than the national average. The median age in Third Lake is 45 which is approximately 21% higher than the Illinois average of 37. In Third Lake, 70% of the population over 15 years of age are married, 94% speak English and 2% speak Spanish. 59% of Third Lake residents were born in Illinois, 33% were born out of state, 2% were born outside of the United States and 7% were foreign born.