Frederick, MD has a population of 68,229 and is the 539th largest city in the United States. The population density is 2,947 per sq mi which is 521% higher than the Maryland average and 3152% higher than the national average. The median age in Frederick is 35 which is approximately 9% lower than the Maryland average of 38. In Frederick, 51% of the population over 15 years of age are married, 77% speak English and 13% speak Spanish. 43% of Frederick residents were born in Maryland, 37% were born out of state, 2% were born outside of the United States and 18% were foreign born.