Eureka is located in St. louis county Missouri with a geographic area of 11.1 square miles. The total population in Eureka is 10,203 with 52.3% male and 47.7% female. Children under age 5 represent 7.4% of the population, under age 18 equal 30.1% of the population and over age 65 is 14.7% of the population. The median household income is $112,750, per capita income is $44,529. There are a total of 3,486 housing units with 82.4% owner occupied. Education includes 16.9% of residents that are high school graduates and 53.1% with a bachelor's degree or higher. The average temperature in Eureka in the summer is 77 degrees, and in the winter 32 degrees.