Series I, “Letters and autographs, 1888-1952, undated,” contains written correspondence and other documents authored or received by members of the Mitchell family. The majority of this series consists of letters authored by Silas Weir Mitchell, but includes items authored by Langdon Mitchell and John Kearsley Mitchell, as well as several items sent by individuals outside the family. This series also includes several non-letter items bearing the signatures of Mitchell family members, including a set of four Mahogony Tree menus which also bear the signatures of other notable Philadelphians. This series is arranged alphabetically by author, and further arranged chronologically.