Incorporated in 1846, the Pennsylvania Railroad Company became the largest railroad in the United States in terms of corporate assets and traffic from the last quarter of the nineteenth century through the mid-twentieth century. This collection of more than 5200 negatives from the official Pennsylvania Railroad files largely depict PRR trains, tracks, equipment, and facilities. The collection also contains numerous views of similar facilities and equipment on other railroads, of nearby buildings and properties, or of standardized equipment and accessories that were collected by the PRR for reference. The negatives were digitized to positives for online access. Most of the digital images seen here are black-and-white, low resolution copies produced from the original negatives. Image: Locomotive 3535.