The papers of the Blackwell family span the years 1759-1960, with the bulk of the material dating from 1845 to 1890. The collection features the papers of Lucy Stone; her husband, Henry Browne Blackwell; and their daughter, Alice Stone Blackwell, all of whom were prominent in the woman's rights movement. Also included are papers of Elizabeth Blackwell, Henry Browne Blackwell's sister who as a doctor pioneered in the role of women in medicine. The collection is arranged in nine series: Alice Stone Blackwell Papers, Elizabeth Blackwell Papers, Henry Browne Blackwell Papers, Kitty Barry Blackwell Papers, Lucy Stone Papers, Other Blackwell Family Papers, Addition, 2022 Addition, and 2024 Addition.

The Elizabeth Blackwell Papers contain extensive diaries, 1836-1908, family and general correspondence, and speeches and writings which document her efforts to open the medical profession to women in the United States and England. Included are numerous letters from Anne Isabella Milbanke Byron, Baroness Byron, and Florence Nightingale who gave support to Blackwell's medical work abroad. Elizabeth Blackwell wrote widely on various aspects of medicine, and her papers include many of her published works unavailable elsewhere.

The Kitty Barry Blackwell Papers include a large group of correspondence which sheds considerable light on Elizabeth Blackwell's years in England. Kitty Blackwell, whom Elizabeth Blackwell adopted in 1854, served as her mother's secretary and companion. Letters from Alice Stone Blackwell in the series contain detailed accounts of the Blackwell family's activities in the United States. In 1921, Kitty Blackwell left England and spent her remaining years with Alice Stone Blackwell.

The papers of Lucy Stone, a leading antislavery and woman's rights advocate, include correspondence with Susan B. Anthony, Henry Ward Beecher, William Lloyd Garrison, Sarah Moore Grimké, Julia Ward Howe, Lydia Mott, Wendell Phillips, and Elizabeth Cady Stanton. Her papers also contain many of her speeches and articles. Included among biographical material are reminiscences by Henry Browne Blackwell and Alice Stone Blackwell.

Henry Browne Blackwell, an enthusiastic reformer, corresponded with many of the leaders in both the woman's rights and the abolition movement. There are also extensive financial papers as well as autobiographical sketches covering the years 1825-1858. Handwritten autobiographical material is accompanied by transcripts made by Alice Stone Blackwell.

The Alice Stone Blackwell Papers include detailed diaries, 1872-1937, which document her interest and work on behalf of woman's rights and other causes. Among her correspondents are Susan B. Anthony, Ekaterina Konstantinovna Breshko-Breshkovskaia, Carrie Chapman Catt, Ricardo Flores Magón, Thomas J. Mooney, Maud Wood Park, and Bartolomeo Vanzetti. One of her major interests was the translation of foreign poetry, and her papers include correspondence with several Armenian, Russian, and Spanish poets, including Gabriela Mistral. A subject file contains drafts and printed versions of most of her translations.

Among the Other Blackwell Family Papers series, perhaps the most outstanding are those of Emily Blackwell and Antoinette Louisa Brown Blackwell. Emily Blackwell followed her sister Elizabeth into the medical profession and was a cofounder of the first woman's hospital staffed by female physicians in the United States. Antoinette Louisa Brown Blackwell was the first woman ordained as a minister in the Congregational Church. She later became a Unitarian. Active in the antislavery, woman's rights, and prohibition movements, Antoinette Blackwell was the author of The Island Neighbors (New York: Harper, 1871), The Sexes Throughout Nature (New York: G. P. Putnam's Sons, 1875), and other works.

The Addition to the papers consists of letters from Alice Stone Blackwell to Armenian author and activist Bedros Arakel Keljik pertaining to the cause of Armenian independence and to Blackwell's translations of Armenian poems; a letter from Emily Blackwell to Elizabeth B. Phelps concerning the need for Phelps to return to work at the New York Infirmary for Women and Children; and a letter from Emma Lawrence Blackwell to her son, Howard L. Blackwell, describing Alice Stone Blackwell's thoughts on the establishment and membership of the Leslie Woman Suffrage Commission and the relocation of Woman's Journal to New York. The addition also includes printed matter relating to the Blackwell family and two unsigned notes which were transferred from the Manuscript Division's Miscellaneous Manuscripts Collection to the Blackwell Family Papers in 1997.

The 2022 Addition consists mostly of incoming correspondence to Blackwell family members and primarily pertains to financial investments, real estate ventures, and the settlement of Emily Blackwell's estate by her executors George W. Blackwell and Elizabeth Cushier. Emily Blackwell explained to her executors how she wanted her estate to be settled and even included instructions for her funeral service. Also present are letters from Anna ("Nannie") Blackwell Huntington, adopted daughter of Emily Blackwell, and her husband, Elon O. Huntington, to Emily Blackwell with updates of family news and financial matters. Letters to Elizabeth Blackwell include correspondence from Amy E. Bell, a financial broker, regarding stocks and from Florence Nightingale offering advice and encouragement in sanitary work. There are also letters from Kitty Barry Blackwell to Alice Stone Blackwell describing Elizabeth Blackwell's death and funeral service.

The 2024 Addition consists of one letter from Emma Lawrence Blackwell to her father, Henry Lawrence, discussing the hiring of an Irish immigrant housekeeper, written while waiting in the office of the Woman's Journal for an appointment with Alice Stone Blackwell.