There was a total of around $168 million of land for sale in New Jersey's Mercer County recently on Land.com. The total acreage of all Mercer County farms and rural land for sale was nearly 1,000 acres. Mercer County ranks 13th out of 21 counties in New Jersey for the combined amount of land currently advertised for sale. Princeton featured the most land for sale. Government and state-level services are the main economic drivers in Mercer County. Mercer County is the 16th biggest county (228 square miles) in New Jersey. It's located in the Central New Jersey region of the state.