Delmarva Power and Light Company is a regulated energy company that provides electricity and natural gas services to customers in the Delmarva Peninsula. These 1926 images document the construction of gas towers and substations at the Christiana and Brandywine power plants in the Wilmington, Delaware.

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.