by Kristen Carney
Updated: August 7, 2025
The most populous counties in Illinois are Cook County with 5,182,617, DuPage County at 937,142, Lake County with 718,604, Will County at 708,583, and Kane County with 520,997. You can get the most current Census population data for all 102 Illinois counties, sorted from the most populous counties in Illinois to the least, according to the 2024 Population Estimates Program.
Sure, you can copy this list right into your favorite spreadsheet tool. Or save yourself formatting headaches and grab the latest Illinois counties population data as a ready-to-use Excel™ file below. It's time to stop searching and start digging into data!
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