Casey is a city in Clark and Cumberland counties in the U.S. state of Illinois. The population was 2,404 at the 2020 census.

Clark County is a county located in the southeastern part of U.S. state of Illinois, along the Indiana state line. As of the 2020 census, the population was 15,455. Its county seat is Marshall. The county was named for George Rogers Clark, an officer who served in the American Revolution.