Second, this stream sits in the shadow of Yellowstone Park, just around the corner from famous Slough Creek and the Lamar. After about 10 miles it changes roads to the Chief Joseph Scenic Highway. This highway runs along the upper section providing plenty of good access. This upper section gives way to a deep, dramatic canyon known as The Box. This canyon begins just below Reef Creek and runs to the National Forest Boundary.
Access here is double tough.
The Clark's Fork of Wyoming. From the community of Clark a rough road comes back up the opposite side. You can take this to the National Forest Boundary and hike down from there. All of this has more to do with walking than fishing, but if that's what you're after, here it is. Past The Box the Clark's Fork passes the mentioned town of Clark, flattens out, slows and moves on toward the Yellowstone River.