Sageville is a city in Dubuque County, Iowa, United States. The population was 95 at the time of the 2020 census, down from 203 in 2000. Sage…Sageville is a city in Dubuque County, Iowa, United States. The population was 95 at the time of the 2020 census, down from 203 in 2000. Sageville is located at 42°33′10″N 90°42′44″W / 42.552850°N 90.712160°W.