The collection is a rich resource for evidence not only on the life of Mary Howitt and her immediate family but on a wide range of social, political, and literary subjects from the mid-nineteenth century. The writers are observant, articulate and frank. The bulk of the correspondence was between women, and inevitably touches closely on domestic issues, including the raising of children, as well as on the role of women themselves. Geographical location is sometimes particularly important, as in the series of letters from Mary's sister Emma Alderson, in Cincinnati, Ohio before the American civil war. The following series comprise the main elements in the collection:
- Correspondence from Mary Howitt to her sister Anna Harrison, 373 Letters, 1822-1882; her niece Mary Harrison, 13 letters, 1847-1883; and unidentified and other correspondents (Ht 1);
- Correspondence from Anna Harrison to her daughters Mary Harrison, 13 letters, 1853-1873, Margaret Yarnell, 7 letters, 1861, and Agnes MacDonnell, 6 letters, 1861; her sister Mary Howitt, 78 letters, 1825-1867; and other correspondents (Ht 4);
- Correspondence from Emma Alderson to her sisters Mary Howitt, 76 letters, 1823-1847, and Anna Harrison, 8 letters, 1824-1847; her mother Ann Botham, 40 letters, 1834-1847; and other correspondents. There are also parts of her American journal (Ht 7);
- Smaller series include correspondence from: William Howitt (Ht 2), Richard Howitt (Ht 3), Daniel Harrison (Ht 5), Hannah Harrison (Ht 6), Harrison Alderson (Ht 8), Charles Botham (Ht 9), Anna Mary Watts (Ht 10), Alfred Howitt (Ht 11), Anna Mary Harrison (Ht 12), Margaret Ann Yarnell (Ht 13), Ellis Yarnell (Ht 14), Agnes MacDonnell (Ht 15), Emily Harrison (Ht 16), Joe (Ht 17), William Alderson (Ht 18), Mildred Yarnell (Ht 19), Agnes Yarnell (Ht 20), miscellaneous items (Ht 21-27), and notes by biographer Amice Lee.