The Fisk family papers are a fragment combining both business and personal papers.

Harvey Fisk is represented by a collection of letters (1846-1890) privately published by his son Harvey Edward in 1896. Fisk was highly observant and articulate from an early age, and his letters to other family members are an equal blend of both social and business life. He begins describing his education at the Bakersfield Academy in Vermont, then his apprenticeship in Trenton and the courtship of Louisa Green, whom he married in 1853. He notes the lure of the California Gold Rush, but his father forbade him to go. He notes the effect of the Panic of 1873 and the difficulties of the C&O financing and his relationship with Collis P. Huntington. Letters from his later years contain some information on his work with government bonds but focus primarily on his travels abroad, notably to Edinburgh, Glasgow, Paris, Biarritz, Carlsbad, Rome and Venice. His deep Puritan roots are revealed by his youthful shock at drinking and card-playing, even among Presbyterians, and by continuing religious homilies in later life. Since the letters were published originally for his children, there is almost no description of the family's domestic life after his marriage.

Fisk & Hatch is represented by a comprehensive financial statement showing its performance for every year of its existence (1862-1885) and by similar accounts with the C&O Railroad.

The firm of Harvey Fisk & Sons is represented by scattered financial statements (1886-188) and by a short synopsis of the firm's history prepared in 1921.

Alex G. Fisk was originally in charge of the Boston office but appears to have moved to New York in the late 1890s after the death of his brother Charles J. His letterbook contains some correspondence relating to the New England business of the firm in 1895 but thereafter deals mostly with household expenditures, the disposition of Charles's home and effects, and a few letters relating to the Union League Club of New York. A letter of Dec. 11, 1896 contains an enthusiastic and unsolicited endorsement of the Eastern Talking Machine Company's gramaphone. The concluding letters of 1901 again deal with placing railroad and municipal bonds in New England.

The letterbook of Charles J. Fisk (1883-1898) combines both business and personal letters. The former reflect his rather routine duties as treasurer. However, there is substantial correspondence on the firm's campaign to have the federal government repurchase its bonds, including letters to Pres. Grover Cleveland and Secretaries of the Treasury C. S. Fairchild and William Windom and subsequent orders for the sale of bonds. There are also some letters from 1898 dealing with the placement of municipal bonds for New York City. The book also contains several letters from Harvey E. to Pliny Fisk describing market conditions and his strategy for riding out the depression of 1893-1896. This contrasts with many lay-off notices for the firm's employees. Many of the letters describe Charles's own business activities, including real estate development at Rockaway Beach in the early 1880s, ventures in New Jersey street railways undertaken with his father-in-law A.G. Richey, a leader of the Trenton bar, cattle breeding, and household expenses. There are also two lists of destitute persons needing work or public relief in Plainfield, New Jersey, in 1893.