Stretching across the Susquehanna River between Harford and Cecil counties, this hydroelectric dam greatly advanced access to electrical power in the surrounding rural area and is still one of the largest nonfederal dams in the United States. The Boston engineering firm of Stone and Webster was hired by Philadelphia Electric Company to design the medium-height, concrete masonry gravity dam and the associated powerhouse and substation. These structures exhibit simplified Art Deco aesthetics that break from use of historicizing details. The dam includes the bridge carrying U.S. 1 across the river because an earlier bridge, as well as the original village of Conowingo, was inundated after its construction.