Part I contains correspondence, journals for the years 1811-1863, some miscellaneous writings, an autograph album, a Sedgwick genealogy, and other papers of Catharine Maria Sedgwick. The majority of the papers cover her adult years. Subjects include family matters; Sedgwick's daily life; her career as a writer; 19th-century social conditions, especially the treatment of orphans, enslaved people, prisoners, and the poor; religion (Unitarianism in particular); theater, art, and music; attitudes toward women; local, national, and foreign political issues; and health and medical developments, such as the treatment of diseases and broken bones, mental health issues, childbirth, and the introduction of ether. The papers also document Sedgwick's travels in the U.S. and abroad, including her observations on economic and social conditions, as well as Sedgwick's relationships with renowned 19th-century authors, political figures, reformers, etc.

Part II contains correspondence, primarily letters from Katharine Sedgwick Minot to her aunt Catharine Maria Sedgwick. Subjects include family, education, American and European literature, social life in Boston and New York, the anti-slavery movement, the Civil War, travel and transportation, the treatment of the mentally ill, and women's rights. Katharine Sedgwick Minot also wrote about her daily activities and those of her husband William Minot (1817-1894), their children, other members of the Sedgwick and Minot families, and prominent Boston friends and acquaintances, including members of the Forbes, Lowell, Longfellow, Howe, Davis, Channing, and Quincy families. William Minot advised Catharine Maria Sedgwick about investments. Some letters describe the construction and furnishing of the Minot family home, "Woodbourne," completed in 1846. Also included is correspondence with Alice Woodbourne Minot, Louisa Davis Minot, Elizabeth Sedgwick Rackemann, and Charles and Elizabeth Dwight Sedgwick.

Many letters discuss Sedgwick's literary career, including topics for novels; the public reception of her work; the admiration of her contemporaries, such as Lucy Aikin, Andrew Combe, Maria Edgeworth, S. Cummings Fitzwilliams, Eliza Cabot Follen, Horace Mann, Harriet Martineau, Elizabeth Palmer Peabody, and John Greenleaf Whittier; her election as an honorary member of the Historical Society of Pennsylvania and the Nu Pi Kappa Literary Society of Kenyon College in Ohio; requests from Harvard University for copies of her works; the sale of Life and Letters of Catharine M. Sedgwick, edited by Mary Dewey; and Charles Sedgwick Rackemann's efforts to publish a new edition of her works in the 1890s.

Among the correspondents are many leading 19th-century ministers, writers, educators, actresses, European political exiles, and others, including Henry W. Bellows, William Cullen Bryant, James Freeman Clarke, Orville Dewey, Charles Follen, John Kenyon, Mary Russell Mitford, Henry Ware, and William Ware. Correspondence with the English actress Fanny Kemble Butler discusses Butler's personal life and marital problems. Also included are lists of Sedgwick's works and other miscellaneous lists, autographs, and fragments.

Part III consists primarily of correspondence between Catharine Maria Sedgwick and her sister-in-law Jane Minot Sedgwick, as well as other relatives and friends. Family members represented include her brothers Theodore (1780-1839), Henry Dwight (1785-1831), Robert, Charles, and their wives; her sister Frances Sedgwick Watson; her nieces Susan Sedgwick Butler, Elizabeth Sedgwick Child, Katharine Sedgwick Minot, Frances Susan Pomeroy, Elizabeth Sedgwick Rackemann, Jane Minot Sedgwick (1821-1889), and Frances Sedgwick Watts; her nephews Theodore (1811-1859), Henry Dwight (1824-1903), and William Ellery Sedgwick; Henrietta Ellery Sedgwick; and Louisa Davis Minot. Also among the correspondents are Edward Tyrrel Channing, Susan Higginson Channing, William Ellery Channing, Lydia Maria Child, William Ellery, and Elizabeth Palmer Peabody.

Subjects include Sedgwick's writing and her attitudes toward publication; the publishing and re-issuing of editions of her work; the support of her family; her views on religion, marriage, and "maidenly independence"; health and old age; travel; her interest in European political exiles, such as Giovanni Albinola, Gaetano de Castillia, and Federico Confalonieri; the financial demands of Penelope Russell Sedgwick after the death of Theodore Sedgwick and other financial matters; the treatment of Henry Dwight Sedgwick (1785-1831) for his mental illness during the 1820s; the treatment of childhood diseases and broken bones; the abolitionist movement in Boston; and the Unitarian Church. The letters document Sedgwick's relationships with other 19th-century literary figures, including William Cullen Bryant, Mary Griffith, Harriet Martineau, and Mary Russell Mitford, as well as her interest in works by contemporary authors Nathaniel Hawthorne and Sir Walter Scott. Correspondence with Eliza Cabot Follen discusses Follen's early romantic interests, her marriage to Charles Follen, various literary works, and Sedgwick's writings.

Also included are fragments, memoranda, notes on Sedgwick's life, receipted bills for her studies at William Payne's school, and a handwritten journal entitled "Female Chronicle," or "Omnia Vanitas" (Box 1, Folder 1), most likely kept by Sedgwick as a young girl.