Records of the Hennessy Company, and its predecessors the D.J. Hennessy Mercantile Company and the Hennessy Mercantile Company, consist largely of financial records, predominantly during the 1910s to 1920s. Also included are a register (1910-1929) of court cases involving the Company, and agreements (1905-1910, 1917-1918) concerning lease/purchase of home furnishings.

There are subgroups of financial records for the Company's Centerville Branch (1913-1917), Butte Wholesale Grocery Company (1916-1924), the Copper City Commercial Company (1896-1931), the Dominant Motor Company (1918-1920), the M.J. Connell Company (1920-1931), and the MacCallum and Cloutier Mercantile Company (1910-1923).