Hydro

The Old Lock Pump House, whose first element was built in 1837, preserves a feature of the old canal, which relied on locks and pumps to move vessels over the low divide of the Delmarva Peninsula between Chesapeake Bay and Delaware Bay. Because there are no large rivers on the peninsula, water had to be pumped uphill to fill the upper canal and locks.

The plant began operation only twenty-six days after Thomas Edison's first steam plant began operating on Pearl Street in New York (NL 46). On September 30, 1882, an Edison "K" type dynamo produced electricity from a water-powered turbine to light three buildings (two paper mills and the H.J. Rogers home), at rate of about 12 1/2 kilowatts. It is the first Edison hydroelectric central station to serve a system of private and commercial customers in North America. The story of its development provides keen insight into the nation's first experiences with the electric light.

The Georgetown Steam Plant, a surprisingly complete and operable steam power plant after a career of nearly seventy-five years, was built in the early 1900s when Seattle's inexpensive hydroelectric power attracted manufacturers. Much of the power produced at this plant operated the streetcars. It marks the beginning of the end of the reciprocating steam engine's domination in the growing field of electrical energy generation for lighting and power.