Brookside, DE has a population of 13,853 and is the 3,023rd largest city in the United States. The population density is 3,510 per sq mi which is 853% higher than the Delaware average and 3774% higher than the national average. The median age in Brookside is 36 which is approximately 9% lower than the Delaware average of 40. In Brookside, 49% of the population over 15 years of age are married, 82% speak English and 11% speak Spanish. 45% of Brookside residents were born in Delaware, 41% were born out of state, 2% were born outside of the United States and 13% were foreign born.