This collection contains medical records and personal papers of John Dexter Treadwell, a prominent physician in Salem, Massachusetts, in the early nineteenth century. The papers include extracts of medical reports, legal documents, correspondence, account books, and papers pertaining to the Massachusetts Medical Society. Also present are papers belonging to John Dexter's father, John Treadwell, a minister in Lynn, Massachusetts, who later resided in Salem.

Folders 1 and 2 contain six volumes of medical information abstracted by John Dexter Treadwell. Also present is a volume of chemical tables relevant to medicine. John Dexter Treadwell was instrumental in reorganizing the Massachusetts Medical Society; Folder 3 contains drafts of the revised by-laws. The account books in Folder 4 include a volume of John Dexter's family expenses, a volume of his expenses while living in Marblehead, and a volume listing medical books and instruments purchased.

Folder 5 contains legal documents pertaining to the purchase or transfer of land or funds. Also present is the draft of a petition to the General Court noting the difficulty of enforcing the ban on travel on the Lord's Day. Folder 6 includes assorted papers and correspondence, the bulk of which are attributable to John Dexter Treadwell and relate to his interests in medicine and religious studies. The earliest papers (1778-1802) are attributable to John Treadwell (1738-1811).

Folder 7 contains one volume of notes on agriculture. This was possibly written by John Goodhue Treadwell, John Dexter's son, who owned a large farm in Topsfield, Massachusetts, and was interested in scientific experimentation in agriculture. Finally, Folder 8 contains receipts of charges incurred by William C. Treadwell while a student at Amherst College between 1832 and 1836. The relationship between William C. Treadwell and John Dexter Treadwell was not established.