1 definition found mount rainier - U.S. Gazetteer (1990) : Mount Rainier, MD (city, FIPS 54275) Location: 38.94148 N, 76.96400 W Population (1990): 7954 (3586 housing units) Area: 1.7 sq km (land), 0.0 sq km (water) Zip code(s): 20712