Knox County is in Western Illinois. Of the 102 counties in the state, 719-square-mile Knox County ranks 23rd by size. Illinois's Knox County includes nearly 1,000 acres of residential land for sale based on recent Land Network data. The combined market value of farms, rural land, hunting land and other land for sale here was $3 million. The average price of residential acreage for sale in Knox County was $205,334. 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.