Dupo is located in St. clair county Illinois with a geographic area of 6.4 square miles. The total population in Dupo is 3,917 with 43.8% male and 56.2% female. Children under age 5 represent 7.6% of the population, under age 18 equal 23.9% of the population and over age 65 is 15.5% of the population. The median household income is $40,049, per capita income is $27,576. There are a total of 1,682 housing units with 72.1% owner occupied. Education includes 41.5% of residents that are high school graduates and 16.3% with a bachelor's degree or higher. The average temperature in Dupo in the summer is 74 degrees, and in the winter 27 degrees.