Series III (formerly Series C)

The mining and railroad papers relate to Lammot du Pont's outside investments. The chief mining enterprise was the Mocanaqua Coal Company, of which du Pont was president in the late 1860s. It was a small mining company near the Wapwallopen Mills in Luzerne County, Pennsylvania. There was a period of instability in the anthracite coal industry, marked by competition and consolidation of firms and attempts to organize the mine workers. The records describe how these trends soon prompted du Pont to sell the company. The Mocanaqua material is chiefly correspondence, much of which is addressed to C.L. Foxwell and C.H. Gallagher, agent, and salesman, respectively, and concerns orders for coal.

Other mining papers describe du Pont's search for soda deposits of soda, sulfur, and saltpeter to manufacture gunpowder. These papers contain analyses of samples, reports on claims, and correspondence, including mentions of interactions with Indigenous Americans. These papers include letters written by frontiersman Boney Earnest (1845-1933).

The railroad papers concern the construction and management of the Wilmington & Reading Railroad, which linked the du Pont mills with the Reading Railroad system, and its reorganization as the Wilmington & Northern in 1877. There is also data on the reorganization of the Berks County Railroad and its subsequent leasing to the Philadelphia & Reading Railroad. The bulk of this material is correspondence about finances and stock matters, but there are also lists of bondholders, proxy statements, reports to stockholders, agreements, and memoranda.