Middletown, DE has a population of 20,045 and is the 2,174th largest city in the United States. The population density is 1,703 per sq mi which is 362% higher than the Delaware average and 1780% higher than the national average. The median age in Middletown is 36 which is approximately 9% lower than the Delaware average of 40. In Middletown, 58% of the population over 15 years of age are married, 89% speak English and 5% speak Spanish. 48% of Middletown residents were born in Delaware, 44% were born out of state, 2% were born outside of the United States and 6% were foreign born.