The records of the Sonora Mining and Milling Company span the years 1897 to 1944. It is a small collection, and some important types of records are missing or incomplete, but the material here favors no particular era of Sonora's life. Included are meetings of minutes, stock ledgers, cancelled stock certificates, correspondence, assessment records, cash journals, check registers, paid checks, and bank books.

Related materials can be found in the records of the King Mining Company.