Castle Hill, California

Castle Hill first appeared as a census designated place in the 2010 U.S. census formed from part of Alamo CDP.^[6]

As of the 2020 census, Castle Hill had a population of 1,271 and a population density of 2,172.6 inhabitants per square mile (838.8/km²).^[7][8] The age distribution was 21.7% under the age of 18, 4.2% aged 18 to 24, 16.8% aged 25 to 44, 29.8% aged 45 to 64, and 27.4% aged 65 or older. The median age was 49.7 years. For every 100 females, there were 93.5 males, and for every 100 females age 18 and over there were 92.8 males age 18 and over.^[7]

The census reported that 99.1% of the population lived in households, no one lived in non-institutionalized group quarters, and 0.9% were institutionalized.^[7] 100.0% of residents lived in urban areas, while 0.0% lived in rural areas.^[9]

There were 455 households, out of which 32.5% had children under the age of 18. Of all households, 70.1% were married-couple households, 4.0% were cohabiting couple households, 16.7% had a female householder with no spouse or partner present, and 9.2% had a male householder with no spouse or partner present. 15.8% of households were one person, and 9.9% were one person aged 65 or older. The average household size was 2.77. There were 365 families (80.2% of all households).^[7][10]

There were 479 housing units at an average density of 818.8 units per square mile (316.1 units/km²). Of these, 455 were occupied and 24 (5.0%) were vacant. Of occupied units, 91.9% were owner-occupied and 8.1% were occupied by renters. The homeowner vacancy rate was 1.6% and the rental vacancy rate was 4.7%.^[7][11]

Castle Hill is in the Walnut Creek Elementary School District and the Acalanes Union High School District.^[12]