The Hope Mining Company of St. Louis was a Missouri-based company with mining operations in Philipsburg, Montana. Records consist primarily of correspondence (1889-1901) between the home office in St. Louis and the mine office at Philipsburg (1889-1901). There is also correspondence with other companies about supplies, annual reports, and financial records.

Frank Sizer was a Helena and Butte, Montana, mining engineer. He managed the Whitlach-Union, Spring Hill, Eclipse-Argo, and Gould mines; worked for Canoll and Martin; and served as a consultant to William A. Clark in his Colusa Parrott law suit and his purchase of the Rosario Mine in Mexico. Collection (1878-1909) includes correspondence, financial records, legal documents, diaries, scrapbooks, clippings, and notebooks.