A total of 1,000 acres were listed for sale in Warren County, Illinois, recently, representing a total value of approximately $6 million in Warren County land and rural real estate for sale. Warren County ranks 57th out of 102 counties in the Prairie State for the total number of acres of land currently advertised for sale. Of all farms, rural land, hunting land and other land for sale in Warren County, Monmouth had the most land for sale. Manufacturing and related services are the largest economic sectors in Warren County. Warren County is Illinois's 49th biggest county (543 square miles). It's located in the Western Illinois region of the state.