This is primarily a collection of letters, with some additional documents, concerning Young's interest in botany, geology, mineralogy, and natural history. There is information about Bowdoin College, where he studied under Parker Cleaveland. There is also much on the natural history of Maine, where he was the State Botanist in 1847-1849, and also on the Bangor Natural History Society. There are materials on Brazil in relation to Young's service there as the U.S. consul to Rio Grande do Sul from 1863 to 1873. There are also letters from his brother, John C. Young, and his sister, Sarah Augusta Young.

Founded in 1743 by Benjamin Franklin, the American Philosophical Society was the first learned society in the United States. For over 250 years, the Society has played an important role in American cultural and intellectual life. Until the mid-nineteenth century, the Society fulfilled the role of a national academy of science, national library and museum, and even patent office. Early members of the Society included Thomas Jefferson, David Rittenhouse, Benjamin Rush, Stephen Peter Du Ponceau, George Washington, and many other figures prominent in American history. The Archives of the American Philosophical Society consists of 192.25 linear feet of material, organized into thirteen record groups dating back to 1743. The Society's archives extensively documents not only the organization's historical development but also its role in American history and the history of science and technology.

John James Audubon (1785-1851), the American Woodsman, is a legendary naturalist and bird artist. His technique of painting North American birds dramatically as they appeared in their natural habitat was a major contribution to the emerging discipline of ornithology in the nineteenth century. His masterpiece, The Birds of America (1827-1838), elephant folio, was followed by a companion text edition, Ornithological Biography (1831-1849), a smaller octavo edition of Birds (1840-1844) and The Viviparous Quadrupeds of North America, published posthumously. This collection of original letters of publication information, ornithology, and some personal notes was sent primarily to Lucy Bakewell Audubon, his wife, from 1826-1834, and to Victor Gifford Audubon, his son, from 1833-1834, 1840-1844, with some sporadic contact with both between 1836-1839. Items in the collection relate to Audubon's Florida, Great Egg Harbor, and Great Pine Forest expeditions but not to his final expedition up the Missouri River. Of particular note, letters of 1833 and 1834 contain references to his response to the Academy of Natural Sciences of Philadelphia president George Ord's attacks on his credibility. A partial journal entry from New Orleans in 1821 and a few letters to other correspondents, including John Bachman, round out the material.

Alexander Dallas Bache (1806-1867) was an important scientific reformer during the early nineteenth century. From his position as superintendent of the United States Coast Survey, and through leadership roles in the scientific institutions of the time, Bache helped bring American science into alignment with the professional nature of its European counterparts. In addition, Bache fostered the reform of public education in America. The Alexander Dallas Bache Collection consists of 91 letters written primarily by Bache. In most cases, these are brief notes replying to letters that are not part of the collection. The majority of items relate to Bache's work as superintendent of the U.S. Coast Survey, including letters of recommendation and introduction, and there is minor correspondence regarding the National Academy of Sciences, scientific matters, his travels in Europe, or personal matters. Of particular interest is the letter from Louis Agassiz in 1856 expressing his view of what the natural history museum of the future should be.

This collection includes letters from, and drafts of letters to, scientists, artists, musicians, soldiers, political figures, and court personages throughout Europe, especially Italy and France. Topics covered range from personal and social affairs to agriculture, botany, geology, natural history, coinage, museum management, politics, weights and measures, current affairs. The collection also includes four diaries, housed separately with manuscript volumes.

The Thomas Jefferson papers contain a large number of correspondence both to and from Jefferson, as well as various other material related to American Revolutionary War and Early Republic. Includes correspondence with Patrick Henry, Charles Willson Peale, Richard Henry Lee, Horatio Gates, David Rittenhouse, Robert Patterson

Robert Maskell Patterson (1787-1854, APS 1809) was a professor of chemistry and natural philosophy at the University of Pennsylvania (1812-1828) and professor of natural philosophy at the University of Virginia (1828-1835). He was director of the U.S. Mint from 1835 to 1851. His father, Robert Patterson, was a revolutionary soldier, professor of mathematics at the University of Pennsylvania (1779-1814), and director of the U.S. Mint (1805-1824).

Letters (including some transcripts and photostats) from and to Vaughan from many American and British correspondents, including: Also personal correspondence and business papers of Benjamin, Charles, Petty, Samuel Sr., Samuel Jr., William, William Oliver, and Sarah Vaughan (2 boxes); lectures, mostly in shorthand (3 vols.); a large number of notes and memoranda on a wide variety of topics, such as agriculture, architecture, astronomy, diplomacy, diseases, dueling, electricity, hieroglyphs, internal improvements, medicine, meteorology, land, manufactures, politics, punctuation, religion, silk-manufacturing, stock-breeding, taxation, Unitarianism, Benjamin Franklin, John Locke, Napoleon I, Joseph Priestley, Bowdoin College, town of Hallowell, Maine; notes on the peace negotiations, 1782-1783; miscellaneous legal papers; genealogy of the Abbott-Vaughan families. For a personal account of the collection, see Mrs. Mary Vaughan Marvin, "The Benjamin Vaughan Papers," APS Proceedings 95 (1951): 246-249.