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Boulder River (Sweet Grass County, Montana) facts for kids

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Boulder River
Boulderriver MT.jpg
A section of the upper Boulder River
Country Park and Sweet Grass County, Montana
Physical characteristics
Main source 45°10′25″N 110°13′31″W / 45.17361°N 110.22528°W / 45.17361; -110.22528 (Boulder River)
River mouth 4,003 feet (1,220 m)
45°51′10″N 109°55′25″W / 45.85278°N 109.92361°W / 45.85278; -109.92361 (Boulder River)
Basin features
River system Yellowstone River

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.


River Location Discharge
East Boulder River near McLeod 80 cu ft/s (2.3 m3/s)
West Boulder River McLeod 189 cu ft/s (5.4 m3/s)
Boulder River Big Timber 563 cu ft/s (15.9 m3/s)


The 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 names

The Boulder River has also been known as: Rivers a Cross, Rivers across, and Rivers-across. And, to distinguish it from the other Boulder River in Montana, it is sometimes called the "East Boulder River" (as it is east of the other) or the "Boulder Fork of the Yellowstone," parallel with the Clark's Fork of the Yellowstone as differentiated from the Clark's Fork River of Western Montana.

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