The Kate Upson Clark Papers include diaries, correspondence, published and unpublished writings (including notes, articles, lectures, and poems), biographical material and memorabilia. Correspondence from and to family, friends, and students includes intimate letters (1914-22) to her sister, Mary Upson Avery, covering personal, family, occupational, and financial matters, and including references to her activities as a Trustee of Wheaton College, persons of varying importance met through lecture engagements, and glimpses into the careers of her sons, Charles Upson and John Kirkland Clark. Her unpublished manuscript, "The Affair of William Strickland & Co.," is an account of charges of "Abolitionist connivance" brought by the booksellers' business in Mobile, Alabama in which her father Edwin Upson, a native of Connecticut, was an associate. Other writings include composition books (1862-67); diaries she kept as an adolescent and young woman (1862-68, 1888); and extensive notes on a European trip (1923-25).