Harrington, DE has a population of 3,688 and is the 7,805th largest city in the United States. The population density is 1,355 per sq mi which is 268% higher than the Delaware average and 1395% higher than the national average. The median age in Harrington is 28 which is approximately 28% lower than the Delaware average of 40. In Harrington, 51% of the population over 15 years of age are married, 91% speak English and 7% speak Spanish. 59% of Harrington residents were born in Delaware, 41% were born out of state, 0% were born outside of the United States and 0% were foreign born.