Jacob Hiltzheimer, farmer and assemblyman, emigrated from Germany to Philadelphia in 1748 and lead a moderately active political and social life. He was a successful farmer and raised select livestock in the city of Philadelphia. He also boarded horses including those of John Penn and George Washington. He served in the Pennsylvania Assembly for 11 consecutive years beginning in 1786. He was an active contributor in civil affairs and took a remarkable enthusiastic interest in events, in persons, and in every day life all of which he wrote down in his diary. As a result of his Revolutionary War and political acquaintances his contacts were numerous. Hiltzheimer's record of social affairs are for the most part routine daily events such as buying and trading horses, attending barbecues and funerals, and drinking punch. However it is his every day accounts that also records significant events such as the Revolutionary War, transactions of the Pennsylvania Assembly, and Philadelphia's yellow fever epidemics, as well as the dealings of significant people including George Washington, Thomas Mifflin, and John Hancock.

These papers include diaries (1777-1782), expense books (1794-1804), notebooks, a commonplace book, drafts of essays, excerpts from minutes of Friends' Monthly Meeting, Tortola (1741-1761), newspaper clippings, sketches, and correspondence. Also included are letters and papers of Mrs. Thornton.

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).