Bird Tail Rock

MT 200, MP 115, 12 Miles Southwest of Simms – South of Augusta

Bird Tail Rock to the southeast was one of the most prominent landmarks along the Benton Road between Fort Benton and Helena. An igneous intrusion about 55 million years old, it acquired its name because it resembled a “bird’s tail erect and spread out in a fan-shape.” Following an old Indian trail, Lieutenant John Mullan built a road past this extraordinary geological feature in July 1860. The rock was located on a steep divide about midway between the Sun River and Dearborn River crossings. At first, Mullan was not sure wagons would be able to traverse the rugged terrain here. But after pulling a two-wheel cart over the divide in 1859, his assistant, P.M. Engel, determined the route “practicable for wagons in its present state.” With the discovery of gold in southwestern Montana in the early 1860s, the road, now known as the Benton Road, was heavily used by freighters and stagecoaches traveling between Fort Benton and Helena. In 1881, a traveler on the road reported that Bird Tail Divide “was more or less dangerous … and perhaps the most trying piece of stage road in northwestern Montana during the winter season, as the snow-drifts frequently obliterate all traces of [it] for miles.”