The 21-month miracle of 89 years ago

CONOWINGO — Maryland Public Television researched, filmed and aired one of their most popular locally-produced documentaries this past year, “Conowingo Dam: Power on the Susquehanna.” The public TV station gained hundreds of new members in the rush to purchase the DVD of the episode and cases of the documentary were sold during the two-day September open house at the facility, in which every single tour was packed beyond capacity, even with extra tours added every 15 minutes. Often touted as an engineering marvel, the hydroelectric dam at Conowingo could equally be described as a construction miracle spanning the Susquehanna River between Harford and Cecil counties. Especially when one considers that construction began March 8, 1926. Exactly 21 months later the main unit, or Unit No, 1, was turned over for the very time on Jan. 31, 1928. It was an incredible feat 89 years ago, when coffer dams were built of boards, before plywood, steam shovels were limited, and horses and oxen were still a major source of “horsepower” during the construction.


To many locals, it is the free bridge with no toll across the river. A bit scary and intimidating with the narrow span at the powerhouse on the Harford side, but still a convenient bridge to cross. To visitors, it is a fascinating masonry gravity dam with soaring art deco architectural details from the impressive castle-like doors to the multi-pane windows. It was on Jan. 31, 1927, that alternating sections of Conowingo’s east cofferdam were completed, exposing the dry riverbed to allow access for construction on the important powerhouse side. Exactly 12 months later to the day, the main unit or generator was turned over for the first time. Over 3,800 workers flocked to the jobsite to be a part of this modern marvel of construction. This would be the last hydroelectric dam built on the Susquehanna River, though it was the first in Maryland. Other dams upstream in Pennsylvania, including Holtwood and Safe Harbor, pre-date the Conowingo Dam and Maryland’s span would be built to supply power to Philadelphia, which was at the time known as the “workshop of the world.” An employment office was opened in Baltimore, with easy access to docks and railroad stations to capture new immigrants to the country as a potential workforce. The plan worked and persons of every color, creed and — to the frustration of many work crew foremen — languages were hired on the spot. A short line railroad was installed from Havre de Grace to the construction site to haul workers and supplies to the dam on multiple runs a day.

Philadelphia Electric Company awarded the $52 million construction contract for dam to Stone & Webster of Boston on Jan. 23, 1925.The Boston firm did the design work while construction began March 8, 1926, by Arundel Corporation of Maryland. When it was completed 21 months later, it was the second-largest hydroelectric project, by power output, in the United States,

immediately after Niagara Falls. Charles Lawson Eglin, the chief engineer for Philadelphia Electric, was the brain trust behind the construction. It was he who determined to build 11 turbine sites, or chutes for the water power to spin turbines, but only seven turbines were installed. The four higher capacity turbine units were added some 50 years later. Sadly, Eglin passed away in February 1928, so he never had the opportunity to see what was essentially his life’s greatest work completed.

Thank you Ron