Calhoun County is a
county located in the
U.S. state of
Illinois. As of the
2010 census, the population was 5,089, making it the third-least populous county in Illinois. Its
county seat is
Hardin. Calhoun County is located at the tip of the peninsula formed by the confluence of the
Mississippi and
Illinois rivers and is almost completely surrounded by water. Often referred to as 'The Island,' Calhoun County is sparsely populated; it has just five municipalities, all of them classified as villages.