There was a total of almost $186 million of land for sale in 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 12th out of 21 counties in the state for the total acreage of land currently advertised for sale. Of all locations in Mercer County with land 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 New Jersey's 16th biggest county (228 square miles). It's located in the Central New Jersey region of the state.