Marlin, PA has a population of 425 and is the 20,525th largest city in the United States. The population density is 469 per sq mi which is 69% higher than the Pennsylvania average and 418% higher than the national average. The median age in Marlin is 59 which is approximately 46% higher than the Pennsylvania average of 41. In Marlin, 71% of the population over 15 years of age are married, 99% speak English and 0% speak Spanish. 90% of Marlin residents were born in Pennsylvania, 8% were born out of state, 1% were born outside of the United States and 1% were foreign born.