The manuscripts of father William Mitchell and daughter Maria Mitchell are not easily separated, and are treated here together. The collection includes William Mitchell's autobiography, his memoir of Judge Walter Folger of Nantucket, astronomical and meteorological observations, lectures, family and other correspondence.

A product of the distinctive culture of reform in antebellum Philadelphia, William Parker Foulke was the scion of the old elite who put a conservative stamp on social change. Trained as an attorney, Foulke spent much of his adult life engaging his deep amateur interest in natural history and mental philosophy and devoting himself to a variety of civic and philanthropic causes, including the colonization of formerly enslaved persons, penal reform, and cultural institutions in his native Philadelphia. The Foulke Papers are the product of the diverse social and intellectual interests of the Philadelphia attorney and philanthropist William Parker Foulke. Consisting primarily of correspondence, notes, and essays, the collection touches on Foulke's many interests. The collection includes numerous lectures delivered by Foulke along with material on the Lancaster County Prison, New York Prison Association, and the Philadelphia Society For Alleviating the Miseries of Public Prisons; notebooks concerning prisons and prisoners, including a 1846-1852 diary, and a listing of prisoners, their race, age, crime, sentence, and observations; a diary concerning the American Colonization Society (1852); a copy of an arctic diary (1853-1854) by John Wall Wilson, in the hand of Isaac Israel Hayes, which recounts much of the journey aboard the brig Advance, commanded by Elisha Kent Kane. There is also a list of buildings (1820-1841) designed by John Haviland, and material on the American Academy of Music, Philadelphia.

This is a collection of letters, letterbooks, account books, scrapbooks, etc., concerning the families of Robert Hare and Thomas Willing. The letters and other documents include early family material, as well as documents written by numerous family relations, and some obviously only collected by them. The Willing family letters (1744-1901) are diverse, concerning family matters, business, society, comments on the Civil War, etc. There are numerous letters from Thomas Willing, many concerning his banking career, as President of the Bank of North America and later at the first Bank of the U.S. The Hare family letters (1724-1965) are more extensive and diverse, including much on travel in the U.S. and elsewhere. There is a letter from Robert Hare Jr. concerning steam engines, and letters from Horace Binney Hare concerning his education at Harvard, 1860, his trip to San Francisco and the west, 1862, and numerous letters written while a soldier in the Civil War. There are many letters from Horace Binney (1780-1875, DAB) to his daughter Esther, who was married to John Innes Clark Hare (1816-1905, DAB), concerning family travel and court cases. There are also letters from outside the family, such as those from Dorothea L. Dix. The bound volumes include, among others: Robert Hare letterbooks (1824-1825, 1841-1857), estate records, and laboratory expense accounts (1818-1860); G. H. Hare's journal or log of cruises aboard the U.S. United States (1841) and U.S. Flint (1845); Horace Binney Hare's 1862 journal of his trip to San Francisco. There are account books and accounts (1754-1795) kept by Thomas Willing; accounts of the controversy over the estate of John Innes Clark; and records of the First Colored Wesley Methodist Church of Philadelphia (receipt book, 1820-1848; minute book, 1827-1844). There are also Philadelphia court records, and minutes of the Common Council of the city, 1832.