Washington County is in Southern Illinois. Of the 102 counties in the Inland Empire, Washington County is 46th in terms of its size (563 square miles). There is around 1,000 acres of residential land for sale in Washington County, Illinois, based on recent Land Network data. The combined market value of farms and rural land for sale here is nearly $4 million. The average price of residential acreage for sale in Washington County was $278,600. Browse all residential land and rural property for sale in Illinois to find residential land and properties that suit your lifestyle needs, from existing residential homes and estates to land ready for future residential-property development.