Boulder River
Tributary of Jefferson River.
(River Mile: 0 to 77)
Launch Interactive Map
The Boulder River forms at the juncture of its south and west forks on the east side of the Continental Divide, north of Butte, Montana. It flows east, then south 77 miles to its confluence with the Jefferson River near Cardwell. Upstream of the town of Boulder, the river runs through a narrow floodplain blanketed with willows, alder, conifers and, to a lesser extent, cottonwoods and aspen. Rainbow trout, brook trout and mountain whitefish are found in this reach of river. Downstream, the floodplain widens and the river meanders through cottonwoods, aspen, and willows. Brown trout dominate the gamefish in the lower 2 miles of the Boulder. Intensive hard rock mining in the drainage in the late 1800’s and early 1900’s left behind acid mine seeps and mill tailings which today still affect the river and fishery below the town of Basin. Portions of the Boulder River have been relocated due to mining, agriculture, and road and railroad building, and it has been subject to riprapping and channel clearance. In low water years, irrigation diversions severely dewater about 12 miles of the lower river. Flows in the river depend primarily on snowpack in the mountains with a number of large springs adding to the river in the lower valley.
Total Length: 77 miles
FWP Region: Region 3
Fishing District: Central Fishing District
