Rathdrum is a city in Kootenai County, Idaho, United States. The population was 9,211 at the 2020 census, up from 6,826 in 2010. It i…Rathdrum is a city in Kootenai County, Idaho, United States. The population was 9,211 at the 2020 census, up from 6,826 in 2010. It is part of the Coeur d'Alene Metropolitan Statistical Area, which includes the entire county. It is named after Rathdrum, a village in County Wicklow, Ireland.