Ronan is a city in Lake County, Montana, United States. It is on the Flathead Indian Reservation. The population was 1,955 at the 2020 c…Ronan is a city in Lake County, Montana, United States. It is on the Flathead Indian Reservation. The population was 1,955 at the 2020 census. The reservation, on which Ronan is located, was created through the July 16, 1855, Hellgate Treaty. It was made between the United States and the Bitterroot Salish, Upper Pend d'Oreille, and Lower Kutenai tribes. The group is now known as the Confederated Salish and Kootenai Tribes.