Affton is a census-designated place (CDP) in St. Louis County, Missouri, United States, near St. Louis. The population was 20,307 at the 2010 census.GeographyAffton is located at 38°33'4" North, 90°19'25" West .According to the United States Census Bureau, the community has a total area of 4.6sqmi, all land.DemographicsAs of the census of 2000, there were 20,535 people, 8,892 households, and 5,655 families residing in the CDP. The population density was 4,480.1 people per square mile (1,731.1/km²). There were 9,128 housing units at an average density of 1,991.5/sq mi (769.5/km²). The racial makeup of the CDP was 97.62% White, 0.06% Black, 0.01% American Indian, 1.30% Asian, 0.03% Pacific Islander, 0.28% from other races, and 1.13% from two or more races. 1.01% of the population were Hispanic or Latino of any race.There were 8,892 households out of which 26.5% had children under the age of 18 living with them, 51.1% were married couples living together, 9.5% had a female householder with no husband present, and 36.4% were non-families. 31.9% of all households were made up of individuals and 14.0% had someone living alone who was 65 years of age or older. The average household size was 2.31 and the average family size was 2.93.
