New castle is located in New castle county Delaware with a geographic area of 3.5 square miles. The total population in New castle is 5,302 with 46.6% male and 53.4% female. Children under age 5 represent 2.8% of the population, under age 18 equal 11.7% of the population and over age 65 is 22.0% of the population. The median household income is $72,951, per capita income is $45,543. There are a total of 2,577 housing units with 61.9% owner occupied. Education includes 36.5% of residents that are high school graduates and 35.5% with a bachelor's degree or higher. The average temperature in New castle in the summer is 74 degrees, and in the winter 35 degrees.