Upper Marlboro, MD has a population of 694 and is the 17,532nd largest city in the United States. The population density is 1,690 per sq mi which is 256% higher than the Maryland average and 1766% higher than the national average. The median age in Upper Marlboro is 41 which is approximately 8% higher than the Maryland average of 38. In Upper Marlboro, 43% of the population over 15 years of age are married, 94% speak English and 4% speak Spanish. 33% of Upper Marlboro residents were born in Maryland, 63% were born out of state, 1% were born outside of the United States and 3% were foreign born.