The Jacob Butler Varnum papers (79 items) contain letters and documents related to Varnum's career as a factor at United States Indian trading posts in Sandusky, Michilimackinac, and Fort Dearborn, Chicago; as a captain in the 40th Massachusetts Infantry during the War of 1812; and as a Washington D.C. merchant after he left government service. The collection is comprised of 59 letters, 1 diary, 13 documents and financial records, and 5 miscellaneous items. Included are letters and instructions from various government officials concerning trade with Indians in Ohio, Michigan, and Illinois, as well as five letters from Varnum to his father Senator Joseph B. Varnum (ca.1751-1821) concerning his activities as factor.
The Correspondence series (60 items) comprises the bulk of the collection. Forty-nine items document Varnum's governmental career spanning 1811 to 1826, during his service as Indian trade factor in Sandusky, Michilimackinac, and Chicago; and as captain of the 40th Massachusetts Infantry during the War of 1812. Varnum received instructions from various Indian agents and government officials concerning the regulation of trade with the Munsee, Ojibwe (Chippewa), Ottawa, Sioux, and Wyandot Indians, among others. Many letters came from the United States Office of Indian Trade at Georgetown, including four from Indian Officer John Mason (1812 and 1815), and 21 letters from Superintendent of Indian Trade Thomas Loraine McKenney (1816-1822). These contain discussions of trade operations, types of merchandise, questions arising about the sale of goods, and instructions for the reporting of financial accounts. Also of note are five letters from Varnum to his father, Joseph Bradley Varnum (1750-1821), in which he described his experiences at Sandusky and at Michilimackinac, as well as with the business of the trading house at Chicago (December 3, 1811; January 14, 1812; May 21, 1816; November 3, 1817; March 1, 1818).
- August 8, 1811: Joseph Bradley Varnum to John Mason, accepting the appointment of his son as agent of the United States Indian trading house at Sandusky, Ohio
- March 1, 1818: Varnum to his father predicting the outbreak of a great war with the Indians "from the Simenoles to the Sioux"
- February 8, 1820: Thomas L. McKenney letter to Jacob B. Varnum, giving instructions about the handling of money given to Varnum by Government Indian agents
Most of the 1823-1826 material concerns government reimbursements for military expenses at Fort Dearborn. The collection contains 11 letters documenting Varnum's post-governmental career as a merchant in Washington D.C. and Petersburg, Virginia (1826-1860).
- February 1827-August 1832: Five items regarding Varnum and John Biddle concerning mutual business interests in Detroit
- December 17, 1833: John H. Kinzie to Varnum concerning Chicago lands owned by Kinzie, a fur trader
The Diary series (1 item) contains a 26-page notebook with Varnum's description of his trip from Chicago to Dracut, Massachusetts, by way of Detroit and Buffalo (August 17-October 22, 1822), and from Detroit through New York and Philadelphia, to Washington D.C. (May 28-June 22, 1823). Varnum reported on his manner of travel (horse, ship, steamboat) and his travel route, describing stops at many of the major towns along the Erie Canal. He commented on the towns that he passed through including Rochester, New York, which had grown considerably since the opening of the Erie Canal (page 6). He also noted prices for room and board. The final five pages contain financial accounts for Varnum's military expenses incurred from 1813 to 1815.
The Documents and Financial Records series (13 items) contains material documenting Varnum's finances and his service in the War of 1812.
- June 8, 1813: Affidavits (and a fragment of the same item) documenting the capture of Joseph B. Varnum's trunks, taken by the British as they were being transported from Michilimackinac to Detroit
- 1814: Six military district orders related to promotions, responsibilities, and discipline in the 40th Massachusetts Infantry, in which Varnum was a captain under Acting Adjutant General George P. Peters
- August 22, 1815: Copy of a bond oath signed by Varnum as factor for Indian trade at Chicago, and a copy of his father, Jacob Butler Varnum's oath of office
- 1816-1827: Four financial records of debts and receipts for goods purchased by Varnum
- Undated : Deposition of Richard Smyth regarding the sale of a lot in Detroit owned by Varnum's father-in-law John Dodemead
The Miscellaneous series (5 items) contains 3 envelope covers, one of which includes a recipe for a "Lazy Daisy" cake (c.1930). Also present are a photograph of a man and two women outside of a tent next to a car (c.1930), and a typed 13-page biography of Joseph Bradley Varnum, undated and unattributed.