The core of this collection consists of interoffice correspondence (1906-1923) between General Managers A.C. Carson, John D. Pope, and Norman B. Braley, in Butte, Montana, and Presidents Thomas F. Cole and Robert Linton and Secretary-Treasurer F.R. Kennedy in Duluth, Minnesota, and New York. The correspondence includes annual and quarterly reports and weekly letters, all describing development work and production in considerable detail. The remainder of the interoffice correspondence deals with general problems of operation of the mines.

The general correspondence (1906-1907, 1914-1926) includes letters with the Anaconda Copper Mining Company about the processing of ore, letters with equipment suppliers, correspondence with other mining companies about labor management issues, applications for employment, letters from former employees inquiring about back pay, World War I letters, and a wide variety of other letters. Of special interest are files of letters inquiring about possible victims of the Granite Mountain and Speculator disasters.

There are two letterpress books of outgoing correspondence (1909-1912), which include weekly letters and quarterly reports to the president. There is one folder of photocopies of outgoing correspondence (1905-1906).

In addition, there are a small number of assay reports, ore shipment statements, and estimates of ore reserves; miscellaneous financial records including invoices, freight bills, taxes, and cost sheets; two agreements (1919, 1920) involving labor relations; lists of mining claims; articles of incorporation, a directors' resolution, and stock certificates; an annual report (1929) [other years are in Library]; subject files; and miscellany.

There is a small subgroup of material concerning the North Butte Mining Company compiled by Al Hooper, including a scrapbook of clippings about the Granite Mountain Mine explosion (1915) and fire (1917).