The Hazard Powder Company was one of the largest gunpowder and explosives manufacturers in the United States in the late-nineteenth century. This group consists of six mounted photographs showing unidentified buildings and the dam at the Hazard Powder Company in Connecticut. An unrelated print shows a covered bridge photographed in winter that crossed the Brandywine River at 16th Street in Wilmington, Delaware.

Mark C. Walker & Son Co. was a general contractor firm in the early to mid-twentieth century. The company was founded as Callahan-Walker Construction Company in Omaha, Nebraska, by Mark Connell Walker (1889-1966) and his father-in-law, William F. Callahan (1856-1930), a railroad contractor. Upon Callahan's death, Walker took on his son, Mark Callahan Walker (1911-1999), as a partner. This album, compiled by Walker Jr., documents construction projects during World War II, as well as the post-war western United States. It highlights the impact of public works in the twentieth century. The album contains photographs, text, and newspaper clippings detailing several key construction projects: the Gary Armor Plate Steel Mill in 1942, the Harlan County Dam between 1946 and 1947, and the Orange County Sanitation Plant in 1953. The album also contains photographs and trade catalogs from the company's Polair Mobile Refrigerator Division, which designed and built refrigerated truck trailers for the U.S. Army.

Pennsylvania Power & Light Company formed in 1920 through the consolidation of eight electric utilities companies serving central and eastern Pennsylvania. The collection primarily includes corporate papers documenting the company’s acquisition of various competing electric companies in the early-to-mid twentieth century by way of franchise building, market research and corporate communications, hydroelectric development through studies and surveys on Pennsylvania’s waterways, and material documenting the company’s various power plants in central eastern Pennsylvania. Financial and accounting records of the Pennsylvania Water & Power Company, which PP&L acquired in 1955, are also included.

This is a small collection of three postcards. Two postcards have images of Pennsylvania Railroad stations in Greensburg and Swissvale, Pennsylvania. The third postcard is an advertisement for Pennsylvania Cement Co. showing the Whitney (N.C.) Dam. The Pennsylvania Railroad (PRR) was chartered in 1846 to completing an all-rail road across the state. In 1857 the Pennsylvania Railroad purchased the old Main Line system and eventually brought the entire line from Philadelphia to Pittsburgh under one management.

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.

Pierre A. Gentieu was a long-term employee of E.I. du Pont de Nemours & Company who created an invaluable photographic record of the company's Brandywine Mills at the turn of the century. E.I. du Pont de Nemours & Company is a chemical company more commonly referred to as the DuPont company. The company was established in 1802 by Pierre Samuel du Pont de Nemours and his son Eleuthère Irénée du Pont the company began with the production of gunpowder. This small collection includes original drymounted photographic prints of views near Henry Clay Village in Delaware by Pierre Gentieu. Several have simple hand drawn decorative borders on them and are signed. There are also several items related to DuPont Gunpowder and rifles.