The records of Day Mines, Inc. span the years 1921 to 1985, with the bulk of the material covering the years 1950 to 1980.

Included are organizational records, correspondence files, financial ledgers, ore production and shipment records, personnel and payroll records, insurance and tax records, records of several joint ventures with other companies, visitor registers for the Day Building, the transcript of a 1952 National Labor Relations Board hearing, and records concerning the sale of building lots in the Western Union Townsite.