Harrisburg is a city in and the county seat of Saline County, Illinois, United States. It is located about 55 miles (88.51392 km) southwest of Evansville, Indiana, and 111 mi (179 km) southeast of St. Louis, Missouri. Its 2020 population was 8,219, and the surrounding Harrisburg Township had a population of 10,037, 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.