Mercer County is in Western Illinois. Of the 102 counties in the state, 363,963-acre Mercer County ranks 44th by size. Recent listings of residential land for sale in Mercer County, Illinois, totals 1,000 acres and a combined market value of about $3 million. The most common type of land for sale by combined acreage in Mercer County is residential property. The average price of residential acreage for sale in Mercer County was $178,085. 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.