Washington County is in Southern Illinois. Of the 102 counties in the Prairie State, Washington County is 46th in terms of its size (563 square miles). Recent Land Network data shows nearly 1,000 acres of residential land and property for sale in Illinois's Washington County, which is valued at a combined $2 million. The average price of residential land for sale in Washington County was $244,850. 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.