These photostats of letters were collected from various repositories by Lyman H. Butterfield for his book, "Letters of Benjamin Rush" 2 v. American Philosophical Society Memoirs 30(1951). Some of the topics discussed are Philadelphia and United States politics, slavery, Afro-American churches, and medicine.

The collection includes letters between Hutchinson and his uncle Israel Pemberton, written while Hutchinson was a student of medicine in London. There are also 12 tickets of admission to medical lectures in Philadelphia and London, including one given by William Hunter, and 3 unused cards of admission to Hutchinson's own lectures. Miscellaneous items include Hutchinson's marriage certificate; genealogical data on the Hutchinson, Hare, and Pemberton families; and stock certificates, 1857-1872, of the McKean and Elk Land and Improvement Company. Materials dated post-1793 are to and from Hutchinson family members.

The papers include miscellaneous letters, letterbooks, books, certificates, and diplomas of various members of the Muhlenberg family. Among them are photostats of letters and papers of General John Peter Gabriel Muhlenberg and officers of the Continental Army on military affairs in the Southern Department during the American Revolution (1772-1804); photostats of letters to Albert Gallatin, Nathanael Greene, Edward Hand, Winthrop Sargent, Baron von Steuben, William Alexander, and George Washington; photostat of General Muhlenberg's journal of trips to the Ohio (1784, 1797); photostats of letters and notes of Gotthilf H. E. Muhlenberg, including a diary kept at Halle (1771) and extracts of thirty letters to Stephen Elliott of Beaufort and Charleston, South Carolina (1808-1815); photostats of letters of Henry A. Muhlenberg about his biography of General Muhlenberg (1848-1849); and photostats of letters of Henry Melchior Muhlenberg (1711-1787). Also included is an original letterbook of Peter Muhlenberg, paymaster of the United States Army, kept at Augusta and Savannah, Georgia (1836-1842). Henry Muhlenberg's notebooks (1784-1813), written in Latin or German script, in a small hand, includes a wealth of botanical observations, with a focus on Lancaster, Pennsylvania. The Henry Muhlenberg journals are a record of daily occurrences, with many features of a commonplace book, containing prescriptions, notes of questions asked candidates for the Lutheran ministry, and the plan of a barn. There is also a biographical account of Rev. Henry Melchior Muhlenberg (1711-1787).