|Clark County Illinois Cities/Towns - Casey, Livingston, Marshall (County Seat), Martinsville, Melrose, Orange, Westfield, West Union
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Clark County is a county located in the U.S. state of Illinois. The U.S. Census Bureau estimates the population in 2016 at 15,938. Its county seat is Marshall.
Clark County was formed in 1819. Clark County was named for George Rogers Clark, an officer of the army of Virginia that captured the Northwest Territory from the British at the close of the Revolutionary War.