A total of around 1,000 acres were listed for sale in Illinois's Mason County recently, representing a combined $6 million in Mason County land for sale. Mason County ranks 85th in the Prairie State for the combined amount of land currently advertised for sale. Of all land and rural real estate for sale in Mason County, Havana featured the most land for sale. Mason County is the 47th largest county (563 square miles) in Illinois. It's located in the Western Illinois region of Illinois.