The Beaverhead–Deerlodge National Forest is the largest of the National Forests in Montana, United States. Covering 3.36 million acres (13,600 km2), the forest is broken into nine separate sections and stretches across eight counties in the southwestern area of the state. President Theodore Roosevelt named the two forests in 1908 and they were merged in 1996. Forest headquarters are located in Dillon, Montana. In Roosevelt's original legislation, the Deerlodge National Forest was called the Big Hole Forest Reserve. He created this reserve because the Anaconda Copper Mining Company, based in Butte, Montana, had begun to clearcut the upper Big Hole River watershed. The subsequent erosion, exacerbated by smoke pollution from the Anaconda smelter, was devastating the region. Ranchers and conservationists alike complained to Roosevelt, who made several trips to the area. (Munday 2001)

The Big Hole River is a tributary of the Jefferson River, approximately 153 miles (246 km) long, in Beaverhead County, in southwestern Montana, United States. It is the last habitat in the contiguous United States for native fluvial Arctic grayling and is a historically popular destination for fly fishing, especially for trout.