Warren County is in Western Illinois. Of the 102 counties in the Prairie State, 543-square-mile Warren County ranks 49th by size. Recent listings of residential land and property for sale in Warren County, Illinois, totals roughly 1,000 acres and a combined market value of nearly $3 million. The most common type of land for sale by combined acreage in Warren County is house. The average price of residential land for sale in Warren County was $249,709. 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.