The value of all farmsand rural real estate for sale in Mercer County, Pennsylvania, recently was $29 million, representing a combined 869 acres of land for sale in Mercer County. Mercer County ranks 44th in the state for the total acreage of land currently advertised for sale. Among cities in Mercer County with farms, hunting land and other rural land and acreage for sale, Greenville featured the most land for sale. Mercer County is the 33rd biggest county (682 square miles) in Pennsylvania. It's located in the Great Lakes & Wilds Pennsylvania region of Pennsylvania.