Marcus L. Hewett was a mine operator, banker, and legislator from Basin, Montana. Records include correspondence, financial records, legal documents, etc. for the Basin Gold and Copper Company (1898-1903); the Cataract Copper Mining Company (1903-1904); the Montana Consolidated Copper Company (1907); the Boston and Alta Copper Company (1909-1911); and the Hewett State Bank (1906-1907).

John Shober (1832-1925) was a Helena, Montana, miner, attorney, and state legislator. Collection (1832-1952) includes descriptions of frontier social and mining conditions. Included are subgroups for Shober's nephew John H. Shober, Jr., manager of a ranch near Townsend; and of his niece Harriet Shober Nolan, wife of Cornelius B. Nolan.

Hubert Simmons (1881-1967) was a Red Lodge, Montana, attorney, state legislator, and coal mine owner. Papers consist of five subgroups: Simmons' personal papers (1906-1967); Eagle Coal Company records (1918-1947); Owl Mining Company records (1930-1958); W.B. Innes and Company records (1919-1930); and Western States Coal Company records (1917-1927).