Philadelphia, PA has a population of 1,559,938 and is the 5th largest city in the United States. The population density is 11,626 per sq mi which is 4095% higher than the Pennsylvania average and 12732% higher than the national average. The median age in Philadelphia is 34 which is approximately 17% lower than the Pennsylvania average of 41. In Philadelphia, 38% of the population over 15 years of age are married, 78% speak English and 10% speak Spanish. 67% of Philadelphia residents were born in Pennsylvania, 16% were born out of state, 4% were born outside of the United States and 13% were foreign born.