Armagh Borough is located in East Wheatfield Township Route 22. Eight families led by James and Margaret Jane Graham from the Counties of Armagh, Antrim, and Ulster arrived in the area in August 1792. Margaret Jane married Mr. Graham after the death of her first husband Lord William Parker. Mr. Graham was the caretaker of Lord Parker's estate. James and Margaret left to escape social pressures against their marriage. In 1880, Joseph McCartney surveyed the town. On October 2, 1804 Armagh had mail service. In June 1805 Armagh Borough established the first Post Office in Indiana County. Thomas Kerr was the postmaster. On April 10, 1834 by Act of General Assembly, Armagh was chartered as a borough. The name means "the field on a hill."