Ravalli County is a county located in the southwestern part of the U.S. state of Montana. Ravalli County is part of a north/south mountain valley bordered by the Sapphire Mountains on the East and the Bitterroot Mountains on the West. It is often referred to as the Bitterroot Valley, which is named for the Bitterroot Flower. As of the 2010 census, the population was 40,212. Its county seat is Hamilton . - Source: Wikipedia