The records of Copper King span the years 1901 to 1949, with the bulk of the material covering the years 1904 to 1944. Included are minutes of meetings, reports to stockholders, assessment records, stockholder correspondence, ledgers, journals, and tax records.

Of particular note in these records are the fifteen assessment ledgers, which are of a number, completeness, and style found nowhere else in the records obtained from Day Mines, Inc. Originally squarish volumes that opened to reveal two distinct sections, the left half was the assessment ledger. The right half was an assessment receipt book, from which the company's record keepers copied the information into the ledger portion. One sample of the redundant assessment receipt books has been retained.