Personal, business, and legal letters; manuscripts including prose, poetry, and diaries; and documents including deeds, receipts, invoices, and account books. The 18th century materials focus on the personal and business correspondence of Calvin, Jotham, and Martin Gay, sons of Ebenezer Gay who were engaged in shipping between New England and the Maritime Provinces. There are occasional letters of Jotham and Martin referring to the American Revolution. The Otis family correspondence of the 18th century, likewise, is of a purely routine and personal nature. There are only four letters of Col. James Otis, and only two of his son, James. Gay and Otis family interests intertwine during the 19th century with the marriage of Mary Allyne Otis to Ebenezer Gay, who are among the chief correspondents of this century, along with their children including Sidney Howard Gay and Winckworth Allan Gay. The Otis correspondence centers around business, real estate, and personal interests of Mary A. Otis Gay's brothers John, Joseph, and William Otis.

The Kent Family Papers contains letters, manuscripts, journals, and documents of the Kent family. The bulk of this material is the papers of James Kent and of William Kent. Also included are autographs, letters, and various ephemera collected by the Kent, Pinckney, and Webster families.

1992-1995 Additions: 138 volumes of his diaries, 1920-1994, have been added, as well as 12 letters from W.A. Craigie concerning new entries for the Oxford English Dictionary, 1 drawing in the style of John Leech, 2 19th century drawings, the manuscript of his "Young John of Gaunt; a poem in fourteen cantos", 22 engraved American portraits, 5 maps of the American Civil and Revolutionary Wars, 3 scrapbooks, World War I to 1976, his commonplace book, 1927-1990, several of his published books, and "The Sheriff's Prisoner", an autobiographical account of his 8 months in Brixton Prison for Obscene Libel on the publication of "Guido and the Girls", along with letters and documents re. this case.