Illinois Population 2017
The population of Illinois in 2016 is estimated at 12,837,801. The 2015 Census estimates put the population at 12,859,995, which was a decrease from the 2014 numbers.
Illinois is one of only 7 states that has a negative growth rate in 2016. At -0.17% per year, it is ahead of only West Virginia. Between 2000 and 2010, the population of Illinois grew by a mere 3.3%, compared to the national average US population growth of 9.7%.
The 2016 population makes Illinois the fifth largest state in the USA based on population.
Chicago, Largest City in Illinois
Most of the Illinois population is based in the North East of the state. Chicago, home to 2,720,546 people, remains the largest city in Illinois. It dwarfs the state's other cities. The next largest is Aurora, with 200,661 people.
This marks one of Illinois' defining features -- although it has a large urban population, it is spread through a number of smaller cities. Including Chicago, there are twelve cities with more than 75,000 people.
Many of these smaller cities make up a part of the Chicago Metropolitan Area (prosaically also known as Chicagoland), which holds between 8.3 and 9.8 million people, depending on how you classify its boundaries.
Cook County is the largest county in Illinois, housing 5,238,216 people. The next largest county is neighboring Dupage, with 933,736 people. Almost half of the Illinois population can be found in just those two counties.