Saline County is a county in Southern Illinois. At the 2020 census, it had a population of 23,768. The largest city and county seat is Harrisburg. This area of Southern Illinois is known locally as "Little Egypt". Three major towns in Saline County are connected by U.S. Route 45, and formerly by the now-abandoned Cairo and Vincennes/Big Four/New York Central Line, from north to south: Eldorado, Harrisburg, and Carrier Mills.