What is the biggest city in Lake County, IL?
Answered by Eshu Chikoti · Licensed Illinois real estate broker, RE/MAX Top Performers
Answered October 8, 2026 · Waukegan
Waukegan is the biggest city in Lake County, Illinois, and it is also the county seat. The 2020 census counted 89,321 residents in Waukegan, and the Census Bureau's estimate for July 1, 2025 is 87,940. The city covers about 24 square miles of land, according to the Census Bureau. As the county seat, Waukegan holds county offices such as the Chief County Assessment Office and the GIS Division, both at 18 North County Street. In the 2010 census, Waukegan counted 89,078 residents, so its size has held roughly steady for over a decade.
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About the author
Licensed Illinois real estate broker, RE/MAX Top Performers
I help people buy, sell and rent homes across Lake County. Each answer here is researched from the sources listed above.