The papers of Harry L. Day span the years 1899 to 1956 with the bulk of the material covering the years 1900 to 1940. Included are correspondence relating to the Hercules Mining company and personal correspondence, records relating to his activities with the State Bank of Commerce, 1905-1936; Federal Mining and Smelting Company, 1912-1921; his property and investments, Wallace Realty Co., and other mining activities. Other papers contain Day's financial records, date books, and an early ore shipment record.

Refoldering the material, combining the contents of less bulky folders, and discarding duplicate material reduced the bulk of this group by five cubic feet.