Also during this period, there are many letters from relatives in North Carolina to Hedrick and Mary Ellen in Washington and from Mary Ellen to relatives and friends. In 1873, there are a few letters from son John A. Hedrick traveling in Europe. On 11 March 1876, there is a letter on Patent Office stationery from Hedrick to Georgetown University tendering his resignation as professor of chemistry and toxicology in the medical faculty. Letters after Hedrick's death are chiefly to Mary Ellen from her children. On 15 January 1891, there is a letter of son Charles J. Hedrick submitting a biographical note on his father to the National Cyclop dia of American Biography.
Undated letters are chiefly family letters, a few clearly from the Chapel Hill area.
Many are drafts of outgoing letters, mostly in Mary Ellen's hand. 36 Undated Series 2. Other Materials 1850s-1900 and undated. About 90 items. Also included is a draft description of a device Mary Ellen Hedrick claimed to have invented to hold hot stove covers and irons, 1868.