The overall value of farmsand rural real estate for sale in Northumberland County, Pennsylvania, recently on Land.com was approximately $36 million. This represents approximately 2,000 acres of farms, rural land, hunting land and other land for sale in Northumberland County. Northumberland County ranks 49th in the Keystone State for the total acreage of land currently advertised for sale. Of all land for sale in Northumberland County, Northumberland featured the most land for sale. Northumberland County is the 48th biggest county (477 square miles) in Pennsylvania. It's located in the Alleghenies & Valleys Pennsylvania region of the state.