An early settler and prominent citizen in the Moravian heartland near Bethlehem, Pennsylvania, Timothy Horsfield was named justice of the peace when Northampton County was formed out of Bucks in 1752, and was one of those given responsibility for the defence of the local white and Christian Indian populations during the French and Indian War. The Horsfield Papers offer a window onto the tumultuous history of northeastern Pennsylvania during the 1750s and 1760s. Comprised largely of correspondence and related documents between Horsfield, William Parsons, and provincial and military authorities, the collection includes important information on the Native tribes' actions (previously described as "Indian assaults") in the region in 1756 and 1757 and the military and diplomatic response of settlers.

Reports on conferences and treaties with the Indians and miscellaneous Indian affairs in Pennsylvania, with emphasis upon the French and Indian War. Correspondents include: John Armstrong Thomas Barton Edward Braddock Daniel Claus George Croghan James Hamilton James Logan Hugh Mercer Andrew Montour Robert Hunter Morris Robert Orme Ferdinand J. Paris Thomas Penn Horatio Sharpe Joseph Shippen William Shirley John Stanwix Robert Stobo William Trent Conrad Weiser

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).