Pike County is a county in the U.S. state of Illinois. It is located between the Mississippi River and the Illinois River in western Illinois. According to the 2020 United States Census, it had a population of 14,739. Its county seat is Pittsfield.

Calhoun County is a county in the U.S. state of Illinois. As of the 2020 census, the population was 4,437, making it Illinois’ third-least populous county. Its county seat and biggest community is Hardin, with a population of 801. Its smallest incorporated community is Hamburg, with a population of 99. Calhoun County is at the tip of the peninsula formed by the courses of the Mississippi and Illinois rivers above their confluence and is almost completely surrounded by water. Calhoun County is sparsely populated; it has just five municipalities, all of them villages.