Fairfield, PA has a population of 535 and is the 19,147th largest city in the United States. The population density is 795 per sq mi which is 187% higher than the Pennsylvania average and 778% higher than the national average. The median age in Fairfield is 52 which is approximately 27% higher than the Pennsylvania average of 41. In Fairfield, 68% of the population over 15 years of age are married, 100% speak English and 0% speak Spanish. 60% of Fairfield residents were born in Pennsylvania, 40% were born out of state, 0% were born outside of the United States and 0% were foreign born.