The records of the Bethlehem Steel Corporation are a series of fragments, lacking the complete runs of corporate and executive documents that normally comprise a business archive. The surviving records give a reasonable overview of the company's history and activities, but one which is lacking in depth.

Correspondence and memorabilia of its executive officers consist largely of material collected by Robert McMath, Vice President (Finance) and Secretary. These include organization papers, directories, annual and quarterly reports to the stockholders and internal statistical reports. McMath’s correspondence deals with an assortment of subjects, including those related to the financial downturn of the 1930s and its effect on business and industry. Other letters pertain to plant visits, construction activities, destruction of securities, financial progress of competing steel companies, investments, the benefits of free enterprise over communism, and Bethlehem’s contribution to World War II. Although the bulk of the letters are addressed to McMath, some are directed to Bethlehem Steel Chairman Eugene G. Grace and Charles Schwab.

There are bound collections of documents regarding major mergers and acquisitions and the issuance of stock and bond issues, these documents are most useful in tracing the evolution of corporate structure. Also from McMath's office are scattered legal files of which the most important is a transcript of testimony from the anti-trust proceedings barring the merger with the Youngstown Sheet & Tube Company in 1968.

The Longwood Gardens series documents the creation and expansion of Longwood Gardens. The photographs of the property are arranged chronologically. They start with a few nineteenth century views of the property when it was the property of the Peirce family who owned it through the legacy of a William Penn land grant and continue through its intensive development under the direction of du Pont who gave personal attention to building fountains, conservatories, and a popular outdoor theater. Though the du Pont’s hosted an annual garden party, there are only images of one garden party from 1915. There are two albums of Longwood Gardens, one dates from 1907 through 1913 and shows the construction of a dam, tree plantings, the formal garden, fountains, and the Peirce-du Pont house renovation. The second album is of photographs by Gould White and dates to the 1920s. The album contains some hand-colored images by M.M. Pugh, particularly of the fountains. There are several sets of postcards that date as early as 1909 through 1931, the largest set of postcards are from 1928. Most of the postcards are black and white, though some are in color. There are glass plate negatives of the gardens and grounds, including the construction of the main conservatory in 1919 and its completion in 1920, as well as images of the mansion, and a set of images of a group of people digging out a snow drift. There are glass stereoview autochromes of the conservatory, gardens, and grounds from around 1922 and 1928, as well as color glass lantern slides of the conservatory in 1924 and garden views in 1937. There are two sets of Dufaycolor glass transparencies of garden views, grounds, and the mansion dating from around 1935-1936. There are also several issues of the newsletters Longwood Chimes and Longwood Gardens Employees, which date from 1985 through 1991.