Land for sale in Union County recently totaled around $11 million and almost 1,000 acres. Union County ranks 62nd in the Independence State for the total number of acres of land currently advertised for sale. Of all land and rural real estate for sale in Union County, Millmont featured the most land for sale. Government and state-level services are the main economic drivers in Union County. Union County is the 64th largest county (317 square miles) in Pennsylvania. It's located in the Alleghenies & Valleys Pennsylvania region of the state.