A Sachem and Civil War adjutant to Ulysses Grant, Ely Samuel Parker was an important figure in the Seneca Indian nation during the first half of the nineteenth century. Trained as an engineer, Parker was deeply involved in the Senecas' land disputes with the Ogden Land Company and he played an important role in interpreting Seneca culture for a white audience, most notably as a consultant for Lewis Henry Morgan. Collected by Arthur C. Parker, the Ely Samuel Parker Papers include correspondence, manuscripts, and printed materials relating primarily to Seneca affairs, history, language, and culture, as well as politics, education, engineering, and the Civil War. Among Parker's correspondents were Henry Clay, Millard Fillmore, Henry M. Flagler, Lewis Henry Morgan, Henry Rowe Schoolcraft, Daniel Webster, and Asher Wright. Several letters relate to Parker's service as engineer of public buildings in Galena, Illinois, and to his Masonic activities. Among the noteworthy items in the collection are several essays on Seneca history and culture, a fragment of Parker's diary, 1847, and a significant quantity of material on the Seneca language assembled by Asher Wright.

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).