The Purcells are shown on some United States maps as the Percell Mountains, where their southern limit protrudes into the states of Idaho and Montana, abutting Lake Koocanusa, a reservoir on the Kootenai River. American geographic classifications consider the Percells to be part of the Rocky Mountains but in Canada that terminology is reserved for ranges on the east side of the Rocky Mountain Trench. In the Purcell Mountains, most of the peaks are near or above 10,000 feet in elevation.