The Boulder River is a tributary of the Yellowstone River, approximately 60 mi (96 km) long, in south central Montana in the United States. It is one of two rivers named the Boulder River in Montana.It rises in the Gallatin National Forest in the Absaroka Range in southern Park County. It flows north through mountainous canyons, a cataract under a natural bridge, and northwest in a widening valley past McLeod. It joins the Yellowstone at Big Timber. The landscape of the Boulder River and river valley has merited the filming of two movies: A River Runs Through It and The Horse Whisperer.TourismThe river is a popular destination for fly fishing. Other attractions in the valley include several church camps, a guest ranch, and several USFS campgrounds. The Forest Service also maintains several guard stations, trailheads, and picnic areas in the valley.Variant namesThe Boulder River has also been known as: Rivers a Cross, Rivers across, and Rivers-across.
