Muir, PA has a population of 496 and is the 19,597th largest city in the United States. The population density is 999 per sq mi which is 260% higher than the Pennsylvania average and 1002% higher than the national average. The median age in Muir is 41 which is approximately 1% higher than the Pennsylvania average of 41. In Muir, 78% of the population over 15 years of age are married, 98% speak English and 1% speak Spanish. 97% of Muir residents were born in Pennsylvania, 3% were born out of state, 0% were born outside of the United States and 0% were foreign born.