Harrisburg ( or ) is a city in and the county seat of Saline County, Illinois, United States. It is located about 57 miles (92 km) southwest of Evansville, Indiana and 111 miles (179 km) southeast of St. Louis, Missouri. The 2010 population was 9,017, and the surrounding Harrisburg Township had a population of 10,790, including the city residents. Harrisburg is included in the Illinois-Indiana-Kentucky Tri-State Area and is the principal city in the Harrisburg Micropolitan Statistical Area with a combined population of 24,913.