1 definition found affton - U.S. Gazetteer (1990) : Affton, MO (CDP, FIPS 280) Location: 38.54945 N, 90.32891 W Population (1990): 21106 (9243 housing units) Area: 12.8 sq km (land), 0.0 sq km (water) Zip code(s): 63123