Armagh, PA has a population of 121 and is the 26,364th largest city in the United States. The population density is 2,108 per sq mi which is 661% higher than the Pennsylvania average and 2227% higher than the national average. The median age in Armagh is 49 which is approximately 20% higher than the Pennsylvania average of 41. In Armagh, 64% of the population over 15 years of age are married, 100% speak English and 0% speak Spanish. 91% of Armagh residents were born in Pennsylvania, 7% were born out of state, 0% were born outside of the United States and 2% were foreign born.