Lake County, Illinois, USA
County or equivalent
Location overview
Lake County occupies the northeastern corner of Illinois between Wisconsin, Cook County and Lake Michigan, with Waukegan as its county seat. Its landscape includes Lake Michigan shoreline, glacial lakes, wetlands, prairies, forest preserves and numerous smaller inland lakes. Created from part of McHenry County in 1839, the county grew through lake ports, roads and rail connections linking Chicago and Milwaukee. Lake County had about 719,000 residents in 2025. Life sciences, manufacturing, finance, retail and tourism shape its economy, alongside Naval Station Great Lakes and extensive commuter ties to Chicago.