Cooper & Hewitt partners were iron businessmen who purchased ironworks, property, and iron mines. In 1845, a rolling mill complex was incorporated as the Trenton Iron Company, and in 1847 iron mines at Andover, New Jersey, were purchased. The records consist of two payroll sheets from 1848, as well as eighty-two inbound letters, mostly from 1849 to 1850. The letters are primarily operating reports from the superintendent of the Andover mine.

The correspondence files of Series I cover such subjects as ordnance contracts with Argentina, Brazil, Chile, Cuba, Italy, Russia and Turkey in the pre-World War I years (circa 1906-1913), general business correspondence and memoranda, sales letters, promotion notices, proposals and inquiries, etc. Correspondence regarding Bethlehem Steel's patent infringement suits with Midland Steel and Niles-Bement-Pond Company (1905-1909) are included. Also covered is the construction of an oil refinery in Argentina and the ore mines in Cuba, Puerto Rico, New York and New Jersey.

These topics generated large amounts of correspondence with a narrow focus. This Johnston filed by subject. In addition, Johnston corresponded with a large number of individuals and companies about a wide range of topics. These letters he filed by correspondent. Some correspondents rated their own individual file, while others, with whom Johnston corresponded infrequently, were grouped together in alphabetical folders. Series I reflects this system. Johnston filed his letters both by subject and by correspondent. Subseries A contains letters filed by correspondent, while Subseries B contains letters filed by subject.

This collection represents materials collected by Cyrus J. Sharer for his research on the iron and steel industry and particularly the world iron ore trade. The main emphasis is on the iron ore trade of the Great Lakes. The period covered, mid-1960s to mid-1980s, was one of crisis and reorganization in the American steel industry and in the lake ore trade, and this is reflected in the records.

The records consist of photocopies of miscellaneous documents of the Empire Steel and Iron Company, the originals of which are in the possession of the National Canal Museum at Easton, Pa. Most of them seem to have come from the Mount Hope site. There is another small collection of miscellaneous materials from the field office of the Mount Hope Mine at the New Jersey Historical Society.

Bethlehem Steel Corporation held foreign interests in ore mines in South America (Argentina and Colombia), Cuba, and Canada. There are forty-eight views of an unidentified refinery (possibly Puerta de la Plata in Argentina) showing interior and exterior views, various buildings and operations. The mostly unidentified Columbian images (late nineteenth and early twentieth century) come from the Maryland Steel Company of Sparrow's Point which had a mine near Nombre de Dios. There are industrial and non-industrial views. The Cuban albums document the Mayari Mines including industrial subjects, scenery, buildings. The one Canadian view is from the Marmoraton Iron Mines in Ontario.

Frederick William Wood (1857-1943) was an executive and engineer in the steel and shipbuilding industries. His papers constitute a major source on the history of the American steel industry in the late nineteenth and early twentieth centuries. The papers are primarily official records of the various companies with which Wood was associated.

John Potts (1760-1809) was a Pennsylvania businessman and member of the Potts family of ironmasters. This collection documents copper and iron ore mining and land speculation in Pennsylvania and Virginia by John Potts Jr. between 1767 and 1830. The bulk of the collection consists of correspondence between Potts and his brother-in-law, Robert E. Hobart (1768-1826). It describes the initial operation of the Keeptryst Furnace and the operations of the Copper Mine Company of Pennsylvania.

Joseph Lincoln Gillson (1895-1964) was the chief geologist for the DuPont Company's Development Department from 1929 to 1960. As chief geologist he traveled all over the world making explorations in search of sulfur, ilmenite, fluorspar, barytes, celestite, and other raw materials, as well as conducting investigations in search of ground water supplies, foundations, and general site studies. This is a small collection that consists of a set of notebooks and related documents from Gillson's time working for the DuPont Company, as well as a set of papers and related documents from consulting projects he did during his retirement.

The Phoenix Steel Company began in the late eighteenth century as a manufacturer of cut nails. It later became a major producer of railroad rails and iron and steel structural members. Their records include minutes (1856-1929); stock ledgers; brief of title papers and property maps; legal and financial correspondence and tax papers; account books; and a works diary.