Pennsylvania Water & Power Company was established to store, transport, and generate water power for both commercial and manufacturing purposes. The Holtwood facility outside of Lancaster, Pennsylvania was the first power plant to have both a hydroelectric generator and a coal power generator. The company was originally called McCall’s Ferry Power Co. and founded in 1905. This small collection consists of photographs that depict the progress of several construction projects at the Holtwood and Safe Harbor plants. Most of these images date from 1951 to 1954, well after the original construction of both sites.

The Pennsylvania Water & Power Company formed in 1910 to finish construction of the Holtwood hydroelectric facility along the lower Susquehanna River in Pennsylvania. The company achieved numerous advancements in hydroelectric and steam power development in the early twentieth century, and helped bring about the electrification of Baltimore and, later, much of the Chesapeake and eastern Pennsylvania area. The records largely consist of correspondence to and from Pennsylvania Water & Power's chief engineer and later president, John Abbet Walls, and other company heads relating to operations, customers, dam construction, and numerous subjects associated with the hydroelectric industry.