A total of around 1,000 acres were listed for sale in Mason County, Illinois, recently; the value of all Mason County farms, rural land, hunting land and other land for sale was around $3 million. Mason County ranks 95th in the Prairie State for the total acreage of land currently advertised for sale. Forest City featured the most land for sale. Mason County is Illinois's 47th biggest county (563 square miles). It's located in the Western Illinois region of Illinois.