The records of the North Pennsylvania Railroad Company consist of corporate records such as minute books, annual reports, account books and statements. They give a good overview of the company's planning, construction and operation down to the Reading lease of 1879, the dull middle period when the firm was a passive lessor (1879-1971), and the complex negotiations connected with the bankruptcy and conveyance to Conrail (1971-1981).

Among the more interesting series are the board papers, which consist of inbound letters and reports directed to the president and board. They include notes on earnings and finances, committee reports, reports of surveys and construction, lists of officers and petitions from patrons. There are many letters from Tom Scott and A.J. Cassatt of the Pennsylvania Railroad regarding arrangements for direct service to the Centennial and use of the New Line. A circular includes a map of the Centennial grounds showing the temporary tracks used to deliver exhibits and construction materials.

The reorganization papers document the company's attempts to find a solvent merger partner, the plan for a Middle Atlantic Rail Corp. (MARC), disputes with SEPTA over the commuter service and subsidy, and the valuation of property conveyed to Conrail.

There are center-line maps of the entire railroad, and track and property maps of most important points. There are also profiles of all the bridges over the Delaware River between Easton and Taylorsville (1875) and of the company's own bridge at Yardley.

Records of other companies include a copy of the charter of the Kensington and Oxford Turnpike Road Company (1836) and records of the associated East Trenton and Delaware & Bound Brook Railroad companies. The latter includes a small selection of president's inbound letters and notices (1878) and a short history of the 1875 Hopewell, New Jersey, "Frog War" between the forces of the D&BB and Pennsylvania Railroad.