This series consists of William Platt Pepper's correspondence to Dorr. Pepper, a lawyer, was Vice President of the Corporation and Managing Director of the Museum from 1876 to 1878, President from 1882 to 1897, "Director" and Vice President from 1898 to 1907. After his death in 1907 the title of the Chief Officer of the Museum was changed from Curator to Director.

Pepper's letters deal with acquisitions (including the acquiring of the Bloomfield Moore Collection), the collection, exhibitions, the staff, Board Meetings, MUseum Committee Meetings, etc. He conducted Museum business from his law office (most of the letters are on stationery indicating he was the Executor of the Estate of Henry Seybert) or from his home at 1730 Chestnut Street. He spent much time discussing the weather and the health of various persons.

Correspondence has been removed from the volumes in which they were originally housed.