Hillandale, Maryland  Hillandale is an unincorporated area and census-designated place located in Montgomery and Prince George's counties, Maryland, United States. Hillandale is contained between the Prince George's / Montgomery County line to the east, the Anacostia River to the west, McCeney Avenue to the north, and D.C.'s Capital Beltway to the south. It borders the communities of Adelphi, Avenel, White Oak and Beltsville. As of the 2010 census, it had a population of 6,043. Hillandale is part of the very large postal designation of Silver Spring. According to the United States Census Bureau, the place has a total area of , all land. In Montgomery County, Hillandale is bordered by the Silver Spring CDP to the south (across the Capital Beltway), the Four Corners CDP to the west (across the Northwest Branch Anacostia River), and the White Oak CDP to the north. In Prince George's County, Hillandale is bordered by the Beltsville CDP to the east (across the Paint Branch) and the Adelphi CDP to the south (across the Capital Beltway). As of the census of 2000, there were 3,054 people, 1,087 households, and 846 families residing in the area. The population density was 2,465.6 people per square mile (950.9/km²). There were 1,110 housing units at an average density of 896.2/sq mi (345.6/km²). The racial makeup of the area was 55.40% White, 25.57% African American, 0.46% Native American, 9.66% Asian, 0.03% Pacific Islander, 5.86% from other races, and 3.01% from two or more races. Hispanic or Latino of any race were 11.39% of the population. There were 1,087 households out of which 27.3% had children under the age of 18 living with them, 66.1% were married couples living together, 7.7% had a female householder with no husband present, and 22.1% were non-families. 16.9% of all households were made up of individuals and 7.9% had someone living alone who was 65 years of age or older. The average household size was 2.80 and the average family size was 3.13.