Coulter is a city in Franklin County, Iowa, United States. The population was 219 at the 2020 census. Coulter got its start in the 1880s, followi…Coulter is a city in Franklin County, Iowa, United States. The population was 219 at the 2020 census. Coulter got its start in the 1880s, following construction of the Chicago & Great Western Railway through that territory.