Jackson County is a county located in the U.S. state of Illinois with a population of 52,974 at the 2020 census, the county is located 98 miles southeast of St. Louis. Its county seat is Murphysboro, and its most populous city is Carbondale, home to the main campus of Southern Illinois University. The county was incorporated on January 10, 1816, and named for Andrew Jackson. The community of Brownsville served as the fledgling county's first seat.