Affiliated companies' records contain a body of records from three companies, the most extensive of which are E.I. du Pont de Nemours & Company of Pennsylvania and E.I. du Pont de Nemours Powder Company. The third company, E.I. du Pont de Nemours Export Company, group of records contains a single minute book and several stock certificates and proxies.

E.I. du Pont de Nemours & Company of Pennsylvania records include merger records, sales records, inventories, financial statements, and correspondence relative to the operation, construction, insurance, safety, and products of the company. Most of the customers were coal mine companies in the Scranton-Wilkes Barre area. Many of the records relate to the Rushdale Magazine at Jermyn, near Scranton, Pennsylvania.

E.I. du Pont de Nemours Powder Company records include administrative, legal, stockholders, and accounting records, along with a small group of miscellany. The administrative papers of the E.I. du Pont de Nemours Powder Company are from the Office of President, T. Coleman du Pont who presided over the firm from 1903 until 1915. These records document the transformation of the Du Pont Powder Company into a modern, centrally administered corporation that would do its own marketing and purchasing and would sell large quantities of all three of the industry's products: black powder, smokeless powder, and dynamite. The records describe the establishment of clear-cut functional departments for sales, purchasing, traffic, engineering, personnel, and accounting. The records also document all aspects of the powder companies' operations during these years: production, sales, personnel, accounting, and the importation of nitrate from Chile. There is also considerable information on the government's investigations leading to the antitrust suit (including correspondence with company attorneys).