Mercer County is in Western Illinois. Of the 102 counties in the Land of Lincoln, Mercer County ranks 44th in terms of size (363,963 acres). The total value of almost 1,000 acres of residential land recently listed for sale in Mercer County, Illinois, was $3 million. The average price of residential acreage for sale in Mercer County was $189,715. 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.