Round Lake is a city located in Lake County Illinois. With a 2020 population of 17,872, it is the 142nd largest city in Illinois and the 2037th largest city in the United States . Round Lake is currently declining at a rate of -0.63% annually and its population has decreased by -2.28% since the most recent census, which recorded a population of 18,289 in 2010. Round Lake reached it's highest population of 18,590 in 2014. Spanning over 6 miles, Round Lake has a population density of 3,215 people per square mile.
The average household income in Round Lake is $99,482 with a poverty rate of 8.12%. The median rental costs in recent years comes to $1,274 per month, and the median house value is $197,800. The median age in Round Lake is 34.6 years, 35.7 years for males, and 34 years for females.