Having two Boulder Rivers in Montana often leads to confusion, with some descriptions mistakenly combine the two. The Boulder River in Southwest Montana begins in Jefferson County, northwest of the town of Boulder. The river flows through a canyon along Interstate 15, at the town, it loops to the south, leisurely meandering through the Boulder Valley until it joins the Jefferson near Cardwell. In late summer, irrigation needs reduce the river's already meager water still further, making fishing and floating difficult. However, in the spring and early summer, the Boulder offers both fishing and floating opportunities, and plays host to brook, brown and rainbow trout. Montana Highway 69 runs through the Boulder Valley from Boulder to Cardwell, providing relatively easy access to the river. With the thriving town of Boulder so close, Highway 69 through the hayfields and timber bottoms of the Boulder Valley is a beautiful drive.