By this period, the Blackfoot and other northern tribes were already armed with guns (see Ewers, 1955, p. 16; Haines, 1938, p. 435), obtained through commerce with the French and English traders of Canada. They had also become mounted, and it may be surmised that the Shoshone lost their equestrian advantage at almost the same time that their enemies acquired guns. Thus the Shoshone retreat from the Canadian plains may well have begun before 1750, as Thompson's narrative indeed suggests (Tyrrell, 1916, pp. 334 ff.). The process was certainly complete by 1805, when Lewis and Clark found the Lemhi River Shoshone hiding in the fastnesses west of the Bitterroot Range and lamenting their loss of the Missouri River buffalo country to better-armed groups. The Shoshone, once masters of the northern Plains, had fallen upon bad times. They complained to the explorers that they were forced to reside on the waters of the Columbia River from the middle of May to the first of September for fear of the Blackfoot, who had driven them out of the buffalo country with firearms (Lewis and Clark, 1904-06, 2:373). Their forays into the Missouri drainage were made only in strength with other Shoshone and their Flathead allies (2:374). The Shoshone apparently were able to utilize areas of Montana adjacent to the Bitterroot Range, for signs of their root-digging activities were seen on the Beaverhead River (2:329-334). This pattern of transmontane buffalo hunting described by Lewis and Clark remained essentially the same until its final end after the establishment of the reservation, and will be described in detail later in this work.