Castle Hills, TX has a population of 4,367 and is the 7,046th largest city in the United States. The population density is 1,769 per sq mi which is 1724% higher than the Texas average and 1852% higher than the national average. The median age in Castle Hills is 48 which is approximately 40% higher than the Texas average of 34. In Castle Hills, 64% of the population over 15 years of age are married, 72% speak English and 26% speak Spanish. 64% of Castle Hills residents were born in Texas, 24% were born out of state, 1% were born outside of the United States and 11% were foreign born.