Lolo Pass, elevation , is a mountain pass in the western United States, in the Bitterroot Range of the northern Rocky Mountains. It is on the border between the states of Montana and Idaho, approximately west-southwest of Missoula, Montana. The pass is the highest point of the historic Lolo Trail, between the Bitterroot Valley in Montana and the Weippe Prairie in Idaho. The trail, known as naptnišaqs, or "Nez Perce Trail" in Salish, was used by Nez Perce in the 18th century, and by the Lewis …