The mountain range covers 135,952 km² (52,491 sq mi).The range is bounded by the Rocky Mountain Trench on the east, and the Kootenai River on the south; their western boundary is the edge of the Interior Plateau.Seventy-five percent of the range is located in Canada and the remaining twenty-five percent in the United States; American geographic classifications place the Columbia Mountains as part of the Rocky Mountains complex, but this designation does not apply in Canada (despite a British Columbia government tourism campaign to rebrand their southern portion as the "Kootenay Rockies").Mount Sir Sandford is the highest mountain in the range, reaching 3,519 metres (11,545 ft).Some geographic classifications also include the Cabinet Mountains and Salish Mountains, which lie south of the Purcells between the Kootenai River and the Clark Fork of the Columbia, but in US classification systems they are generally considered to be part of the Rocky Mountains.