Armstrong County is in Pittsburgh & Countryside Pennsylvania. Of the 67 counties in the Keystone State, 663-square-mile Armstrong County ranks 34th by size. The total value of 1,000 acres of residential land recently listed for sale in Armstrong County, Pennsylvania, was around $12 million. The average price of residential acreage for sale in Armstrong County was $536,756. Browse all residential land and rural property for sale in Pennsylvania to find residential land and properties that suit your lifestyle needs, from existing residential homes and estates to land ready for future residential-property development.