Our Documentary Heritage showcases holdings drawn from the vast collections of the Pennsylvania State Archives.

Early twentieth-century proponents of hydroelectricity favored this type of power for a number of reasons: its cost is relatively low, water is a renewable resource, and it does not cause pollution since it does not use fossil fuels. In addition, hydroelectric plants are in operation longer than fossil fuel facilities, require fewer workers, and have lower maintenance costs.

A photograph of the Holtwood Hydroelectric Power Plant, located in Lancaster County, is drawn from Water Resources Inventory Including Reports, Correspondence, Photographs and Maps, 1913-1920, (series 6.45) in Record Group 6, Records of the Department of Forests and Waters held by the Pennsylvania State Archives. The Water Supply Commission was created in 1905 and operated as an independent agency until it merged with the Department of Forests in 1923 to form the Department of Forests and Waters. Its purpose was to regulate encroachments upon the Commonwealth’s waterways, except for the tidal waters of the Delaware River and its navigable tributaries.

The Holtwood Hydroelectric Power Plant, the first hydroelectric power plant built on the lower Susquehanna River, was constructed by the Pennsylvania Water and Power Company between 1905 and 1910. The first two generators went online in 1911, followed by one unit each in 1912, 1913, and 1914. The initial five generators and an additional two units installed by 1924 yielded a total output of 107.2 megawatts. In 1987, the American Society of Mechanical Engineers designated Holtwood as an International Historic Engineering Landmark for the installation, in 1912, of the world’s first Kingsbury thrust bearing on Turbine Number 5. This supports the entire weight of the rotating components of the turbine and generator totaling approximately 220 tons. Since then, the thrust bearings invented by Albert Kingsbury (1863-1943), a mechanical engineer and college professor, have been installed on all the turbines at Holtwood. The original 1912 Kingsbury bearing on Turbine Number 5 is still in service.

The Kingsbury thrust bearing replaced earlier roller thrust bearings which rarely lasted more than two months before they needed to be repaired. Kingsbury’s thrust bearing consists of a flat cast iron ring called the runner that rests on six pie-shaped flat shoes that match the shape of the ring. The entire bearing is pivot-mounted and immersed in 570 gallons of oil. The rotating motion of the cast iron runner squeezes oil between itself and the shoes; the oil actually supports the combined weight of the equipment and the downward force of the water passing through the turbine, so that there is no actual physical contact between the runner and the shoes.

The files of Record Group 6 contain extensive correspondence and photographs depicting dozens of small-scale hydroelectric plants associated with low-head dams erected on rivers and streams throughout the Commonwealth during the second decade of the twentieth century.


Willis L. Shirk Jr. is an archivist for the Pennsylvania State Archives.