High Quality Content by WIKIPEDIA articles! The Conowingo Dam (also Conowingo Hydroelectric Plant, Conowingo Hydroelectric Station) is a large hydroelectric dam in the Lower Susquehanna River. The dam, one of the largest non-federal hydroelectric dams in the US, is classified as a medium height, masonry gravity type dam. The dam is located in Maryland, spanning the Cecil and Harford county border — 9.9 miles (16 km) from the river mouth at the Chesapeake Bay, about 5 miles (8 km) south of the Pennsylvania border and 45 miles (72 km) northeast of Baltimore.