Saint Mary's County is a county in Maryland. It covers 765 square miles (489,306 acres), which represents less than one percent of the state total. Of the 24 counties in Maryland, Saint Mary's County ranks 12th in terms of the size of its population (0, according to 2015 Census estimates). Recent data from Lands of America calculates the average value of land for sale in Saint Mary's County at $39,672 per acre. The average listing price was $425,742 (the most expensive listing being for $1.8 million) and the median land-parcel size was less than an acre. Land for sale in Saint Mary's County totaled 129 acres and $5.1 million in overall land value, with the city of Leonardtown featuring the most land for sale in the county. Hunting land was the most common type of land for sale in Saint Mary's County.