Railroad logging was an important facet of the history of Montana's lumber industry. The Big Blackfoot Railroad was one of several logging railroads created to sustain the Anaconda Copper Mining Company's sawmill at Bonner. Built by the Chicago, Milwaukee, St. Paul and Pacific (Milwaukee Road) Railroad between 1911 and 1936, the line was used almost exclusively by the Anaconda Company.

The company acquired 625,000 acres of timber in the Blackfoot River Valley in 1904 to provide lumber and cord wood for its mining and smelting operations in Butte and Anaconda. For twenty-eight years, the company harvested approximately 40 million board feet of lumber annually from its property in the valley - making the Anaconda Company the largest timber producer in Montana.

This section of railroad grade was constructed in 1934. By the early 1940's however, economic depression, war and increasing use of trucks to haul lumber caused a sharp decline in the logging industry in the valley.

Although the Anaconda Company ceased logging operations in the Blackfoot Valley in 1949, the line was not abandoned until 1978. Since the line was never intended to be permanent and was often relocated to take advantage of new timber stands, the track was frequently place directly on the ground without the benefit of ballast or any significant grading. Portions of the old railroad can be seen adjacent to the highway to the south.

Erected by Montana Department of Transportation.