- elevation 7,339 ft (2,237 m) - elevation 4,278 ft (1,304 m) Source Continental Divide Trail | Length 124 km | |
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- location Boulder Mountains, Beaverhead-Deerlodge National Forest | ||
The Boulder River is a 77-mile (124 km) tributary of the Jefferson River in southwestern Montana in the United States.
Map of Boulder River, Cardwell, MT, USA
It rises in the Rocky Mountains at the continental divide in the Beaverhead-Deerlodge National Forest in western Jefferson County. It flows east and southeast through the mountains past Boulder, then south to join the Jefferson near Cardwell.
Game fish in the river include brook, brown, and rainbow trout, and mountain whitefish. Brown trout are most prevalent in the last 2 miles (3 km), near the mouth, and the other three species are more prevalent in the reach upstream of the town of Boulder. The lowermost 12 miles (19 km) of the river is affected by irrigation withdrawals, and the reach below the community of Basin is affected by seepage from old mines and tailings.