Mostly routine business correspondence. For 1902 and 1903 there are letters from speculators hoping to buy the Hercules. In 1909 there are many letters to and from Fred T. DuBois in Washington, D.C. about the proposed lead tariff. In 1918 and 1919 there are letters from former employees asking about the Liberty Bonds they had purchased while working for the Hercules. Post-1919 correspondence is mainly between Harry Day, Henry Day, and W.H. Hoover of the office staff regarding routine office matters. Throughout there are letters between the company and its lawyers concerning lawsuits as well as routine legal matters; job applications; letters of reference for former employees; and letters from people looking for relatives believed to be working at the mine. There are also copies of salary scales, dividend records, accident reports, contracts, assay reports, a blueprint and description of the Hercules Mine dated 1892, and reports on the treating of timber at the mine. Arranged chronologically throughout, except for two folders of correspondence with the Coeur d'Alene Iron Works, Jan.-June 1913 and July-Dec. 1913. Appendix 1 is an alphabetical list of correspondents.